Engineering the sensitivity of macroscopic physical systems to variations in the fine-structure constant [CL]

http://arxiv.org/abs/2305.11264


Experiments aimed at searching for variations in the fine-structure constant $\alpha$ are based on spectroscopy of transitions in microscopic bound systems, such as atoms and ions, or resonances in optical cavities. The sensitivities of these systems to variations in $\alpha$ are typically on the order of unity and are fixed for a given system. For heavy atoms, highly charged ions and nuclear transitions, the sensitivity can be increased by benefiting from the relativistic effects and favorable arrangement of quantum states. This article proposes a new method for controlling the sensitivity factor of macroscopic physical systems. Specific concepts of optical cavities with tunable sensitivity to $\alpha$ are described. These systems show qualitatively different properties from those of previous studies of the sensitivity of macroscopic systems to variations in $\alpha$, in which the sensitivity was found to be fixed and fundamentally limited to an order of unity. Although possible experimental constraints attainable with the specific optical cavity arrangements proposed in this article do not yet exceed the present best constraints on $\alpha$ variations, this work paves the way for developing new approaches to searching for variations in the fundamental constants of physics.

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B. Zjawin, M. Bober, R. Ciuryło, et. al.
Mon, 22 May 23
17/60

Comments: N/A

What can a GNOME do? Search targets for the Global Network of Optical Magnetometers for Exotic physics searches [CL]

http://arxiv.org/abs/2305.01785


Numerous observations suggest that there exist undiscovered beyond-the-Standard-Model particles and fields. Because of their unknown nature, these exotic particles and fields could interact with Standard Model particles in many different ways and assume a variety of possible configurations. Here we present an overview of the Global Network of Optical Magnetometers for Exotic physics searches (GNOME), our ongoing experimental program designed to test a wide range of exotic physics scenarios. The GNOME experiment utilizes a worldwide network of shielded atomic magnetometers (and, more recently, comagnetometers) to search for spatially and temporally correlated signals due to torques on atomic spins from exotic fields of astrophysical origin. We survey the temporal characteristics of a variety of possible signals currently under investigation such as those from topological defect dark matter (axion-like particle domain walls), axion-like particle stars, solitons of complex-valued scalar fields (Q-balls), stochastic fluctuations of bosonic dark matter fields, a solar axion-like particle halo, and bursts of ultralight bosonic fields produced by cataclysmic astrophysical events such as binary black hole mergers.

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S. Afach, D. Tumturk, H. Bekker, et. al.
Thu, 4 May 23
55/60

Comments: 22 pages, 12 figures, submitted to Annalen der Physik

High-Frequency Gravitational Wave Detection via Optical Frequency Modulation [CL]

http://arxiv.org/abs/2304.10579


High-frequency gravitational waves can be detected by observing the frequency modulation they impart on photons. We discuss fundamental limitations to this method related to the fact that it is impossible to construct a perfectly rigid detector. We then propose several novel methods to search for O(MHz-GHz) gravitational waves based on the frequency modulation induced in the spectrum of an intense laser beam, by applying optical frequency demodulation techniques, or by using optical atomic clock technology. We find promising sensitivities across a broad frequency range.

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T. Bringmann, V. Domcke, E. Fuchs, et. al.
Mon, 24 Apr 23
21/41

Comments: 11 pages, 3 figures

Variation of the quadrupole hyperfine structure and nuclear radius due to an interaction with scalar and axion dark matter [CL]

http://arxiv.org/abs/2304.04469


Atomic spectroscopy is used to search for the space-time variation of fundamental constants which may be due to an interaction with scalar and pseudo-scalar (axion) dark matter. In this letter, we study the effects which are produced by the variation of the nuclear radius and electric quadrupole moment. The sensitivity of the electric quadrupole hyperfine structure to both the variation of the quark mass and the effects of dark matter exceeds that of the magnetic hyperfine structure by 1-2 orders of magnitude. Therefore, the measurement of the variation of the ratio of the electric quadrupole and magnetic dipole hyperfine constants is proposed. The sensitivity of the optical clock transitions in the Yb$^+$ ion to the variation of the nuclear radius allows us to extract, from experimental data, limits on the variation of the hadron and quark masses, the QCD parameter $\theta$ and the interaction with axion and scalar dark matter.

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V. Flambaum and A. Mansour
Tue, 11 Apr 23
52/63

Comments: N/A

Fine-structure transitions of Si and S induced by collisions with atomic hydrogen [CL]

http://arxiv.org/abs/2304.02727


Using a quantum-mechanical close-coupling method, we calculate cross sections for fine structure excitation and relaxation of Si and S atoms in collisions with atomic hydrogen. Rate coefficients are calculated over a range of temperatures for astrophysical applications. We determine the temperature-dependent critical densities for the relaxation of Si and S in collisions with H and compare these to the critical densities for collisions with electrons. The present calculation should be useful in modeling environments exhibiting the [S i] 25 {\mu}m and [S i] 57 {\mu}m far-infrared emission lines or where cooling of S and Si by collisions with H are of interest.

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P. Yan and J. Babb
Mon, 10 Apr 23
5/36

Comments: Accepted for publication in MNRAS

Extended atomic data for oxygen abundance analyses [SSA]

http://arxiv.org/abs/2304.02310


As the most abundant element in the universe after hydrogen and helium, oxygen plays a key role in planetary, stellar, and galactic astrophysics. Its abundance is especially influential on stellar structure and evolution, and as the dominant opacity contributor at the base of the Sun’s convection zone it is central to the discussion around the solar modelling problem. However, abundance analyses require complete and reliable sets of atomic data. We present extensive atomic data for O I, by using the multiconfiguration Dirac-Hartree-Fock and relativistic configuration interaction methods. Lifetimes and transition probabilities for radiative electric dipole transitions are given and compared with results from previous calculations and available measurements. The accuracy of the computed transition rates is evaluated by the differences between the transition rates in Babushkin and Coulomb gauges, as well as by a cancellation factor analysis. Out of the 989 computed transitions in this work, 205 are assigned to the accuracy classes AA-B, that is, with uncertainties less than 10%, following the criteria defined by the National Institute of Standards and Technology Atomic Spectra Database. We discuss the influence of the new log(gf) values on the solar oxygen abundance and ultimately advocate $\log\epsilon_{\mathrm{O}}=8.70\pm0.04$.

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W. Li, P. Jönsson, A. Amarsi, et. al.
Thu, 6 Apr 23
70/76

Comments: 13 pages, 5 figures; Accepted for publication in Astronomy & Astrophysics

Atomic Data Assessment with PyNeb: Radiative and Electron Impact Excitation Rates for [Fe II] and [Fe III] [GA]

http://arxiv.org/abs/2304.01298


We use the PyNeb 1.1.16 Python package to evaluate the atomic datasets available for the spectral modeling of [Fe II] and [Fe III], which list level energies, A-values, and effective collision strengths. Most datasets are reconstructed from the sources, and new ones are incorporated to be compared with observed and measured benchmarks. For [Fe III], we arrive at conclusive results that allow us to select the default datasets, while for [Fe II], the conspicuous temperature dependency on the collisional data becomes a deterrent. This dependency is mainly due to the singularly low critical density of the $\mathrm{3d^7\ a\,^4F_{9/2}}$ metastable level that strongly depends on both the radiative and collisional data, although the level populating by fluorescence pumping from the stellar continuum cannot be ruled out. A new version of PyNeb (1.1.17) is released containing the evaluated datasets.

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C. Mendoza, J. Méndez-Delgado, M. Bautista, et. al.
Wed, 5 Apr 23
12/62

Comments: 16 Tables, 16 Figures. Atoms, Vol. 11, page 63

Quasi-Molecular mechanism of cosmological recombination: a scheme of calculation [CEA]

http://arxiv.org/abs/2304.00072


For a quasi-molecular mechanism of cosmological recombination, a scheme of calculation based on a rigorous quantum-mechanical approach is elaborated. The probability of free-bound radiative transition into an excited state of a quasi-molecule temporarily formed by a colliding electron and two nearest neighboring protons is derived in a closed algebraic form.

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T. Kereselidze, I. Noselidze and Z. Machavariani
Tue, 4 Apr 23
90/111

Comments: 10 pages, 2 figures

A Long-Baseline Atom Interferometer at CERN: Conceptual Feasibility Study [CL]

http://arxiv.org/abs/2304.00614


We present results from exploratory studies, supported by the Physics Beyond Colliders (PBC) Study Group, of the suitability of a CERN site and its infrastructure for hosting a vertical atom interferometer (AI) with a baseline of about 100 m. We first review the scientific motivations for such an experiment to search for ultralight dark matter and measure gravitational waves, and then outline the general technical requirements for such an atom interferometer, using the AION-100 project as an example. We present a possible CERN site in the PX46 access shaft to the Large Hadron Collider (LHC), including the motivations for this choice and a description of its infrastructure. We then assess its compliance with the technical requirements of such an experiment and what upgrades may be needed. We analyse issues related to the proximity of the LHC machine and its ancillary hardware and present a preliminary safety analysis and the required mitigation measures and infrastructure modifications. In conclusion, we identify primary cost drivers and describe constraints on the experimental installation and operation schedules arising from LHC operation. We find no technical obstacles: the CERN site is a very promising location for an AI experiment with a vertical baseline of about 100 m.

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G. Arduini, L. Badurina, K. Balazs, et. al.
Tue, 4 Apr 23
100/111

Comments: 51 pages, 39 figures, version with higher resolution figures available from this https URL

Understanding the temperatures of H3+ and H2 in diffuse interstellar sightlines [GA]

http://arxiv.org/abs/2303.16070


The triatomic hydrogen ion H3+ is one of the most important species for the gas phase chemistry of the interstellar medium. Observations of H3+ are used to constrain important physical and chemical parameters of interstellar environments. However, the temperatures inferred from the two lowest rotational states of H3+ in diffuse lines of sight – typically the only ones observable – appear consistently lower than the temperatures derived from H2 observations in the same sightlines. All previous attempts at modelling the temperatures of H3+ in the diffuse interstellar medium failed to reproduce the observational results. Here we present new studies, comparing an independent master equation for H3+ level populations to results from the Meudon PDR code for photon dominated regions. We show that the populations of the lowest rotational states of H3+ are strongly affected by the formation reaction and that H3+ ions experience incomplete thermalisation before their destruction by free electrons. Furthermore, we find that for quantitative analysis more than two levels of H3+ have to be considered and that it is crucial to include radiative transitions as well as collisions with H2. Our models of typical diffuse interstellar sightlines show very good agreement with observational data, and thus they may finally resolve the perceived temperature difference attributed to these two fundamental species.

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J. Bourlot, E. Roueff, F. Petit, et. al.
Wed, 29 Mar 23
47/73

Comments: N/A

Optical ultra-stable optical clock cavities as resonant mass gravitational wave detectors in search for new physics [CL]

http://arxiv.org/abs/2301.08200


We propose to use table-top-size ultra-stable optical cavities from the state-of-the-art optical atomic clocks as bar gravitational wave detectors for the frequencies higher than 2 kHz. We show that 2-20 kHz range of gravitational waves’ spectrum can be accessed with instruments below 2 meters in size. The proposed cavities’ materials and properties are being within the present-day technology grasp. The ultra-stable optical cavities allow detecting not only predicted gravitational wave signals from such sources as binary neutron star mergers and post-mergers, subsolar-mass primordial black-hole mergers, and collapsing stellar cores, but can reach new physics beyond standard model looking for ultralight bosons such as QCD axions and axion-like particles formed through black hole superradiance.

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M. Narożnik, M. Bober and M. Zawada
Fri, 20 Jan 23
13/72

Comments: N/A

Plasma broadening of autoionizing resonances [SSA]

http://arxiv.org/abs/2301.07734


A general formulation is developed to demonstrate that atomic autoionizing (AI) resonances are broadened and shifted significantly due to plasma effects across bound-free continua. The theoretical and computational method presented accounts for broadening mechanisms: electron collisional, ion microfields (Stark), thermal Doppler, core excitations, and free-free transitions. {\it Extrinsic} plasma broadening redistributes and shifts AI resonance strengths while broadly preserving naturally {\it intrinsic} asymmetries of resonance profiles. Integrated oscillator strengths are conserved as resonance structures dissolve into continua with increasing electron density. As exemplar, the plasma attenuation of photoionization cross sections computed using the R-matrix method is studied in neon-like Fe~XVII in a critical range $N_e = 10^{21-24}$cc along isotherms $T = 1-2 \times 10^6$K, and its impact on Rosseland Mean opacities. The energy-temperature-density dependent cross sections would elicit and introduce physical features in resonant processes in photoionization, \eion excitation and recombination. The method should be generally applicable to atomic species in high-energy-density (HED) sources such as fusion plasmas and stellar interiors.

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A. Pradhan
Fri, 20 Jan 23
62/72

Comments: 5 pages, 3 figures

Population of ground and lowest excited states of Sulfur via the dissociative recombination of SH+ in the diffuse interstellar medium [IMA]

http://arxiv.org/abs/2212.13538


Our previous study on dissociative recombination of ground state SH$^+$ into $^2\Pi$ states of SH is extended by taking into account the contribution of $^4\Pi$ states recently explored by quantum chemistry methods. Multichannel quantum defect theory is employed for the computation of cross sections and rate coefficients for dissociative recombination, but also for vibrational excitation. Furthermore, we produce the atomic yields resulting from recombination, quantifying the generation of sulfur atoms in their ground (\mbox{$^3$P}) and lowest excited (\mbox{$^1$D}) states respectively.

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J. Boffelli, F. Gauchet, D. Kashinski, et. al.
Thu, 29 Dec 22
4/47

Comments: 9 pages, 8 figures, 3 tables

Bound state properties and positron annihilation in the negatively charged Ps$^{-}$ ion. On thermal sources of annihilation $γ$-quanta in our Galaxy [CL]

http://arxiv.org/abs/2212.03723


The total energy and other bound state properties of the ground (bound) $1^{1}S$-state in the Ps$^{-}$ ion are determined to very high accuracy. Our best variational energy for the ground state in this ion equals $E$ = -0.262005070232980107770402018838 $a.u.$ For this three-body ion we have evaluated (to very high accuracy) the rates of two-, three-, four- and five-photon annihilation. We also discuss some problems which currently exist in accurate computations of the rate of one-photon annihilation $\Gamma_{1 \gamma}$. Highly accurate computations of a number of singular and quasi-singular bound state properties in the Ps$^{-}$ ion are also performed and discussed. By investigating the sources of annihilation $\gamma-$quanta in the universe we have arrived to the conclusion about the high-temperature limit in optics. This can be formulated by the following statement: due to the electromagnetic instability of the vacuum, it is impossible to see (directly) any object heated to temperatures above 350 – 400 $keV$. In reality, instead of such an object an observer will see only an intense flow of annihilation $\gamma-$quanta, electrons and positrons. This phenomenon can be called the annihilation shielding of overheated matter and it is of great interest in Galactic astrophysics.

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A. Frolov
Thu, 8 Dec 22
29/63

Comments: N/A

An efficient Monte Carlo model for the slowing down of photoelectrons. Application to H-$α$ in exoplanet atmospheres [EPA]

http://arxiv.org/abs/2211.14128


Photoelectrons, the fast electrons produced in the photoionization of planetary atmospheres, drive transformations in the atmospheric gas that are often inhibited by energy considerations for thermal electrons. The transformations include excitation and ionization of atoms and molecules, which affect the detectability of these gases and constrain the fraction of incident stellar radiation that transforms into heat. To gain insight into these important questions, we build a Monte Carlo model that solves the slowing down of photoelectrons in a gas with arbitrary amounts of H and He atoms and thermal electrons. Our novel multi-score scheme differs from similar tools in that it efficiently handles rare collisional channels, as in the case of low-abundance excited atoms that undergo superelastic and inelastic collisions. The model is validated and its performance demonstrated. Further, we investigate whether photoelectrons might affect the population of the excited hydrogen H(2) detected at some exoplanet atmospheres by transmission spectroscopy in the H-$\alpha$ line. For the ultra-hot Jupiter HAT-P-32b, we find that photoelectron-driven excitation of H(2) is inefficient at the pressures probed by the line core but becomes significant (yet sub-dominant) deeper in the atmosphere where the line wings form. The contribution of photoelectrons to the destruction of H(2) either by collisional deexcitation or ionization is entirely negligible, a conclusion likely to hold for exoplanet atmospheres at large. Importantly, photoelectrons dominate the gas ionization at the altitudes probed by the H-$\alpha$ line, a fact that will likely affect, even if indirectly, the population of H(2) and other tracers such as metastable helium. Future modeling of these excited levels should incorporate photoelectron-driven ionization.

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A. Muñoz
Mon, 28 Nov 22
54/93

Comments: Accepted for publication in Icarus

Towards an electrostatic storage ring for fundamental physics measurements [CL]

http://arxiv.org/abs/2211.08439


We describe a new table-top electrostatic storage ring concept for $30$ keV polarized ions at frozen spin condition. The device will ultimately be capable of measuring magnetic fields with a resolution of 10$^{-21}$ T with sub-mHz bandwidth. With the possibility to store different kinds of ions or ionic molecules and access to prepare and probe states of the systems using lasers and SQUIDs, it can be used to search for electric dipole moments (EDMs) of electrons and nucleons, as well as axion-like particle dark matter and dark photon dark matter. Its sensitivity potential stems from several hours of storage time, comparably long spin coherence times, and the possibility to trap up to 10$^9$ particles in bunches with possibly different state preparations for differential measurements. As a dark matter experiment, it is most sensitive in the mass range of 10$^{-10}$ to 10$^{-19}$ eV, where it can potentially probe couplings orders of magnitude below current and proposed laboratory experiments.

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C. Brandenstein, S. Stelzl, E. Gutsmiedl, et. al.
Thu, 17 Nov 22
37/63

Comments: 5 pages, 4 figures, contribution to the proceedings of the 8th International Symposium on Symmetries in Subatomic Physics (SSP2022)

A limit on variations in the fine-structure constant from spectra of nearby Sun-like stars [SSA]

http://arxiv.org/abs/2211.05150


The fine structure constant, $\alpha$, sets the strength of the electromagnetic force. The Standard Model of particle physics provides no explanation for its value, which could potentially vary. The wavelengths of stellar absorption lines depend on $\alpha$, but are subject to systematic effects owing to astrophysical processes in stellar atmospheres. We measured precise line wavelengths using 17 stars, selected to have almost identical atmospheric properties to those of the Sun (solar twins), which reduces those systematic effects. We found that $\alpha$ varies by $\lesssim$50 parts-per-billion (ppb) within 50 parsecs from Earth. Combining the results from all 17 stars provides an empirical, local reference for stellar measurements of $\alpha$ with an ensemble precision of 12 ppb.

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M. Murphy, D. Berke, F. Liu, et. al.
Fri, 11 Nov 22
3/58

Comments: 33 pages, 6 figures. Published in Science (11 November 2022). This is the accepted version which includes 20 pages of Supplementary Materials

Space-time variation of the s and c quark masses [CL]

http://arxiv.org/abs/2211.03325


Space-time variation of fundamental physical constants in expanding Universe is predicted by a number of popular models. The masses of second generation quarks are larger than first generation quark masses by several orders of magnitude, therefore space-time variation in quark masses may significantly vary between each generation. We evaluate limits on variation in the s and c quark masses from Big Bang nucleosynthesis, Oklo natural nuclear reactor, Yb+, Cs and Rb clock data. The construction of 229Th nuclear clock is expected to enhance these limits by several orders of magnitude. Furthermore, constraints are obtained on an oscillating scalar or pseudoscalar cold dark matter field, as interactions of the field with quarks produce variations in quark masses.

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V. Flambaum and P. Munro-Laylim
Tue, 8 Nov 22
32/79

Comments: N/A

R-matrix electron-impact excitation data for the H- and He-like ions with Z=6-30 [CL]

http://arxiv.org/abs/2210.13427


Plasma models built on extensive atomic data are essential to interpreting the observed cosmic spectra. H-like Lyman series and He-like triplets observable in the X-ray band are powerful diagnostic lines to measure the physical properties of various types of astrophysical plasmas. Electron-impact excitation is a fundamental atomic process for the formation of H-like and He-like key diagnostic lines. Electron-impact excitation data adopted by the widely used plasma codes (AtomDB, CHIANTI, and SPEX) do not necessarily agree with each other. Here we present a systematic calculation of electron-impact excitation data of H-like and He-like ions with the atomic number Z=6-30 (i.e., C to Zn). Radiation damped R-matrix intermediate coupling frame transformation calculation was performed for each ion with configurations up to $n=6$. We compare the present work with the above three plasma codes and literature to assess the quality of the new data, which are relevant for current and future high-resolution X-ray spectrometers.

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J. Mao, G. Zanna, L. Gu, et. al.
Tue, 25 Oct 22
44/111

Comments: ApJS accepted

ExoMol line lists — {XLVI}: Empirical rovibronic spectra of silicon mononitrate (SiN) covering the 6 lowest electronic states and 4 isotopologues [EPA]

http://arxiv.org/abs/2210.12477


Silicon mononitride ($^{28}$Si$^{14}$N, $^{29}$Si$^{14}$N, $^{30}$Si$^{14}$N, $^{28}$Si$^{15}$N) line lists covering infrared, visible and ultraviolet regions are presented. The \name\ line lists produced by ExoMol include rovibronic transitions between six electronic states: \XS, \AS, \BS, \DS, \asi, \bsi. The \ai\ potential energy and coupling curves, computed at the multireference configuration interaction (MRCI/aug-cc-pVQZ) level of theory, are refined for the observed states by fitting their analytical representations to 1052 experimentally derived SiN energy levels determined from rovibronic bands belonging to the $X$–$X$, $A$–$X$ and $B$–$X$ electronic systems through the MARVEL procedure. The SiNful line lists are compared to previously observed spectra, recorded and calculated lifetimes, and previously calculated partition functions. SiNful is available via the \url{www.exomol.com} database.

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M. Semenov, N. Clark, S. Yurchenko, et. al.
Tue, 25 Oct 22
69/111

Comments: N/A

ExoMol line lists — XLVII. Rovibronic molecular line list of the calcium monohydroxide radical (CaOH) [EPA]

http://arxiv.org/abs/2210.12480


Any future detection of the calcium monohydroxide radical (CaOH) in stellar and exoplanetary atmospheres will rely on accurate molecular opacity data. Here, we present the first comprehensive molecular line list of CaOH covering the \A–\X\ rotation-vibration-electronic and \X–\X\ rotation-vibration bands. The newly computed OYT6 line list contains over 24.2 billion transitions between 3.2 million energy levels with rotational excitation up to $J=175.5$. It is applicable to temperatures up to $T=3000$~K and covers the 0\,–\,35\,000~cm$^{-1}$ range (wavelengths $\lambda > 0.29$~$\mu$m) for rotational, rotation-vibration and the \A–\X\ electronic transition. The strong band around 16\,000~cm$^{-1}$ ($\lambda = 0.63$~$\mu$m) is likely to be of interest in future astronomical observations, particularly in hot rocky exoplanets where temperatures can become extremely high. The OYT6 line list has been generated using empirically-refined \X\ and \A\ state potential energy surfaces, high-level \textit{ab initio} transition dipole moment surfaces and a rigorous treatment of both Renner-Teller and spin-orbit coupling effects, which are necessary for correctly modelling the CaOH spectrum. Post-processing of the CaOH line list has been performed so as to tailor it to high-resolution applications, i.e.\ by replacing calculated energy levels with more accurate empirically-derived values (where available), hence improving the accuracy of the predicted line positions in certain regions. The OYT6 line list is available from the ExoMol database at this http URL and the CDS astronomical database.

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A. Owens, A. Mitrushchenkov, S. Yurchenko, et. al.
Tue, 25 Oct 22
95/111

Comments: N/A

ExoMol line lists — XLV. Rovibronic molecular line lists of calcium monohydride (CaH) and magnesium monohydride (MgH) [EPA]

http://arxiv.org/abs/2210.12474


New molecular line lists for calcium monohydride ($^{40}$Ca$^{1}$H) and magnesium monohydride ($^{24}$Mg$^{1}$H) and its minor isotopologues ($^{25}$Mg$^{1}$H and $^{26}$Mg$^{1}$H) are presented. The rotation-vibration-electronic (rovibronic) line lists, named \texttt{XAB}, consider transitions involving the \X, \A, and \BBp\ electronic states in the 0–30\,000~cm$^{-1}$ region (wavelengths $\lambda > 0.33$~$\mu$m) and are suitable for temperatures up to 5000 K. A comprehensive analysis of the published spectroscopic literature on CaH and MgH is used to obtain new extensive datasets of accurate rovibronic energy levels with measurement uncertainties and consistent quantum number labelling. These datasets are used to produce new spectroscopic models for CaH and MgH, composed of newly empirically-refined potential energy curves and couplings in/between the different electronic states (e.g.\ spin-orbit, electronic angular momentum, Born-Oppenheimer breakdown, spin-rotation, $\Lambda$-doubling) and previously published \textit{ab initio} transition dipole moment curves. Along with Einstein $A$ coefficients, state lifetimes and Land\’e $g$-factors are provided, the latter being particularly useful as CaH and MgH can be used to probe stellar magnetic fields. Computed energy levels have been replaced with the more accurate empirical values (if available) when post-processing the line lists, thus tailoring the line lists to high resolution applications. The \texttt{XAB} line lists are available from the ExoMol database at this http URL and the CDS astronomical database.

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A. Owens, S. Dooley, L. McLaughlin, et. al.
Tue, 25 Oct 22
96/111

Comments: N/A

Searching for scalar field dark matter with hyperfine transitions in alkali atoms [CL]

http://arxiv.org/abs/2210.08778


Fundamental constants such as masses and coupling constants of elementary particles can have small temporal and spatial variations in the scalar field dark matter model. These variations entail time oscillations of other constants, such as the Bohr and nuclear magnetons, Bohr radius and the hyperfine structure constant. In the presence of an external magnetic field, these oscillations induce hyperfine transitions in atoms and molecules. We determine the probability of magnetic dipole hyperfine transitions, caused by the oscillating fundamental constants, and propose an experiment that could detect the scalar field dark matter through this effect. This experiment may be sensitive to the scalar field dark matter with mass in the range $1\,\mu\text{eV}<m_\phi<100\,\mu\text{eV}$.

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V. Flambaum, A. Mansour, I. Samsonov, et. al.
Tue, 18 Oct 22
20/99

Comments: 10 pages, 2 figures

Probing Galactic variations in the fine-structure constant using solar twin stars: systematic errors [SSA]

http://arxiv.org/abs/2210.08276


Sun-like stars are a new probe of variations in the fine-structure constant, $\alpha$, via the solar twins approach: velocity separations of close pairs of absorption lines are compared between stars with very similar stellar parameters, i.e. effective temperature, metallicity and surface gravity within 100K, 0.1 dex and 0.2 dex of the Sun’s values. Here we assess possible systematic errors in this approach by analysing $\gtrsim$10,000 archival exposures from the High-Accuracy Radial velocity Planetary Searcher (HARPS) of 130 stars covering a much broader range of stellar parameters. We find that each transition pair’s separation shows broad, low-order variations with stellar parameters which can be accurately modelled, leaving only a small residual, intrinsic star-to-star scatter of 0-33 m/s (average $\approx$7 m/s, $\approx$10$^{-4}$\r{A} at 5000\r{A}). This limits the precision available from a single pair in one star. We consider potential systematic errors from a range of instrumental and astrophysical sources (e.g. wavelength calibration, charge transfer inefficiency, stellar magnetic activity, line blending) and conclude that variations in elemental abundances, isotope ratios and stellar rotational velocities may explain this star-to-star scatter. Finally, we find that the solar twins approach can be extended to solar analogues – within 300K, 0.3 dex and 0.4 dex of the Sun’s parameters – without significant additional systematic errors, allowing a much larger number of stars to be used as probes of variation in $\alpha$, including at much larger distances.

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D. Berke, M. Murphy, C. Flynn, et. al.
Tue, 18 Oct 22
64/99

Comments: 18 pages, 12 figures. Accepted by MNRAS. The VarConLib (Varying Constants Library) software used in this work is available at this https URL The measurements and results in this work are available at this https URL

Probing Galactic variations in the fine-structure constant using solar twin stars: methodology and results [SSA]

http://arxiv.org/abs/2210.08275


The rich absorption spectra of Sun-like stars are enticing probes for variations in the fine-structure constant, $\alpha$, which gauges the strength of electromagnetism. While individual line wavelengths are sensitive to $\alpha$, they are also sensitive to physical processes in the stellar atmospheres, which has precluded their use so far. Here we demonstrate a new, differential approach using solar twins: velocity separations between close pairs of transitions are compared across stars with very similar physical properties, strongly suppressing astrophysical and instrumental systematic errors. We utilise 423 archival exposures of 18 solar twins from the High-Accuracy Radial velocity Planetary Searcher (HARPS), in which calibration errors can be reduced to $\lesssim$3 m/s. For stars with $\approx$10 high signal-to-noise ratio spectra ($\ge$200 per pixel), velocity separations between pairs are measured with $\approx$10 m/s statistical precision. A companion paper assesses a range of systematic error sources using 130 stars, with a greater range of stellar parameters, providing accurate corrections for astrophysical effects and a residual, intrinsic star-to-star scatter of 0-13 m/s. Within these uncertainties, we find no evidence for velocity separation differences in 17 transition pairs between solar twins. In a second companion paper, this is found to limit local ($\lesssim$50 pc) variations in $\alpha$ to $\approx$50 parts per billion, $\sim$2 orders of magnitude less than other Galactic constraints.

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D. Berke, M. Murphy, C. Flynn, et. al.
Tue, 18 Oct 22
88/99

Comments: 15 pages, 5 figures. Accepted by MNRAS. The VarConLib (Varying Constants Library) software used in this work is available at this https URL The measurements and results in this work are available at this https URL

Formation of primordial helium: a rapid and simple scheme of calculation [CEA]

http://arxiv.org/abs/2209.04644


A rapid and relatively simple scheme of calculation is elaborated and applied to cosmological recombination of helium. Employing the nonrelativistic Coulomb Green’s function, a wavefunction of a colliding electron is represented in an integral form applicable for calculations. Bound electrons of helium are described by the Hartree-Fock wavefunctions. The free-bound transition probabilities into excited states of helium, and the probabilities of bound-bound transitions in helium are calculated in different modes. It is revealed that free-bound transition probabilities weakly depend on to what extent a field experienced by a colliding electron deviates from the purely Coulomb field with charge Z=1, whereas these probabilities strongly depend on the choice of a wavefunction of a bound active electron involved in recombination.

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T. Kereselidze, Z. Machavariani and I. Noselidze
Tue, 13 Sep 22
73/85

Comments: 10 pages, 7 figures

Laboratory Constraints on the Neutron-Spin Coupling of feV-scale Axions [CL]

http://arxiv.org/abs/2209.03289


Ultralight axion-like particles can contribute to the dark matter near the Sun, leading to a distinct, stochastic signature in terrestrial experiments. We search for such particles through their neutron-spin coupling by re-analyzing approximately 40 days of data from a K-$^3$He co-magnetometer with a new frequency-domain likelihood-based formalism that properly accounts for stochastic effects over all axion coherence times relative to the experimental time span. Assuming that axions make up all of the dark matter in the Sun’s vicinity, we find a median 95% upper limit on the neutron-spin coupling of $2.4 \times 10^{-10}$ GeV$^{{-1}}$ for axion masses from 0.4 to 4 feV, which is about five orders of magnitude more stringent than previous laboratory bounds in that mass range. Although several peaks in the experiment’s magnetic power spectrum suggest the rejection of a white-noise null hypothesis, further analysis of their lineshapes yields no positive evidence for a dark matter axion.

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J. Lee, M. Lisanti, W. Terrano, et. al.
Thu, 8 Sep 22
6/77

Comments: 23 pages, 15 figures

Current challenges in the physics of white dwarf stars [SSA]

http://arxiv.org/abs/2209.02846


White dwarfs are a class of stars with unique physical properties. They present many challenging problems whose solution requires the application of advanced theories of dense matter, state-of-the-art experimental techniques, and extensive computing efforts. New ground- and space-based observatories will soon provide an increasingly detailed view of white dwarf stars and reveal new phenomena that will challenge our models. This review is an introduction for researchers who are not in the field of white dwarf astrophysics with the intent to entice them to contribute their expertise to advance our knowledge of these exotic stars. We discuss a wide variety of currently unsolved or partially resolved problems that are broadly related to equations of state, transport processes and opacities.

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D. Saumon, S. Blouin and P. Tremblay
Thu, 8 Sep 22
7/77

Comments: Review article to appear in Physics Reports. 108 pages of text, 33 figures, 372 references

One-Electron Quantum Cyclotron as a Milli-eV Dark-Photon Detector [CL]

http://arxiv.org/abs/2208.06519


We propose using trapped electrons as high-$Q$ resonators for detecting meV dark photon dark matter. When the rest energy of the dark photon matches the energy splitting of the two lowest cyclotron levels, the first excited state of the electron cyclotron will be resonantly excited. A proof-of-principle measurement, carried out with one electron, demonstrates that the method is background-free over a 7.4 day search. It sets a limit on dark photon dark matter at 148 GHz (0.6 meV) that is around 75 times better than previous constraints. Dark photon dark matter in the 0.1-1 meV mass range (20-200 GHz) could likely be detected at a similar sensitivity in an apparatus designed for dark photon detection.

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X. Fan, G. Gabrielse, P. Graham, et. al.
Tue, 16 Aug 22
29/74

Comments: 6 pages, 5 figures

AtoMEC: an open-source average-atom Python code [CL]

http://arxiv.org/abs/2206.01074


Average-atom models are an important tool in studying matter under extreme conditions, such as those conditions experienced in planetary cores, brown and white dwarfs, and during inertial confinement fusion. In the right context, average-atom models can yield results with similar accuracy to simulations which require orders of magnitude more computing time, and thus they can greatly reduce financial and environmental costs. Unfortunately, due to the wide range of possible models and approximations, and the lack of open-source codes, average-atom models can at times appear inaccessible. In this paper, we present our open-source average-atom code, atoMEC. We explain the aims and structure of atoMEC to illuminate the different stages and options in an average-atom calculation, and facilitate community contributions. We also discuss the use of various open-source Python packages in atoMEC, which have expedited its development.

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T. Callow, D. Kotik, E. Kraisler, et. al.
Fri, 3 Jun 22
6/57

Comments: 9 pages, 8 figures. Submitted to Proceedings of the 21st Python in Science Conference (SciPy 2022)

Near K-Edge Photoionization and Photoabsorption of Singly, Doubly, and Triply Charged Silicon Ions [CL]

http://arxiv.org/abs/2204.08750


Experimental and theoretical results are presented for double, triple, and quadruple photoionization of Si$^+$ and Si$^{2+}$ ions and for double photoionization of Si$^{3+}$ ions by a single photon. The experiments employed the photon-ion merged-beams technique at a synchrotron light source. The experimental photon-energy range 1835–1900 eV comprises resonances associated with the excitation of a $1s$ electron to higher subshells and subsequent autoionization. Energies, widths, and strengths of these resonances are extracted from high-resolution photoionization measurements, and the core-hole lifetime of K-shell ionized neutral silicon is inferred. In addition, theoretical cross sections for photoabsorption and multiple photoionization were obtained from large-scale Multi-Configuration Dirac-Hartree-Fock (MCDHF) calculations. The present calculations agree with the experiment much better than previously published theoretical results. The importance of an accurate energy calibration of laboratory data is pointed out. The present benchmark results are particularly useful for discriminating between silicon absorption in the gaseous and in the solid component (dust grains) of the interstellar medium.

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S. Schippers, S. Stock, T. Buhr, et. al.
Wed, 1 Jun 22
57/65

Comments: submitted to The Astrophysical Journal, 13 pages, 7 figures, 4 tables

Anthropic constraint on transient variations of fundamental constants [CL]

http://arxiv.org/abs/2202.04228


The anthropic principle implies that life can emerge and be sustained only in a narrow range of values of fundamental constants (FCs). We extend the anthropic arguments to a regime of transient variations of FCs. Such regime is characteristic of clumpy dark matter models where inside the clumps FCs can reach values vastly different from their everyday values. We show that the passage of such a macroscopic clump through Earth would make Earth uninhabitable. The periodic table of elements is truncated and water fails to serve as a universal solvent. Anthropic principle enables us to improve existing astrophysical bounds on certain dark matter model couplings by five orders of magnitude.

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V. Dergachev, H. Tan, S. Varganov, et. al.
Mon, 25 Apr 22
31/36

Comments: 16 pages, 14 figures

The flux ratio of the [N II]$λλ$ 6548, 6583 Å lines in sample of Active Galactic Nuclei Type 2 [GA]

http://arxiv.org/abs/2204.10036


In spectra of the Active Galactic Nuclei (AGNs), the [N II] 6548, 6583 A lines are commonly fitted using the fixed intensity ratio of these two lines (R[N II]=I${6583}$/I${6548}$). However, the used values for fixed intensity ratio are slightly different through literature. There are several theoretical calculations of the transition probabilities which can be used for the line ratio estimation, but there are no experimental measurements of this ratio, since the [N II] lines are extremely weak in laboratory plasma. Therefore, the intensity ratio of [N II] lines can be measured only in the spectra of astrophysical objects. However, precise and systematic measurements have not be done so far, because of difficulties in measurement of the [N II] ratio in various spectra (overlapping with H$\alpha$, weak intensity of [N II], influence of the continuum noise and outflow contribution, etc.). Here we present the measurements of the flux ratio of the [N II]$\lambda\lambda$ 6548, 6583 A emission lines for a sample of 250 Type 2 AGNs spectra taken form Sloan Digital Sky Survey (SDSS) data base. The spectra are chosen to have high signal-to-noise ratio and to [N II] and H$\alpha$ lines do not overlap. The obtained mean flux ratio from measurements is 3.049 $\pm$ 0.021. Our result is in agreement with theoretical result obtained by taking into account the relativistic corrections to the magnetic dipole operator.

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I. Dojčinović, J. Kovačević-Dojčinović and L. Popović
Fri, 22 Apr 22
3/64

Comments: Accepted in Advances in Space Research, 8 pages, 4 figures, 1 table

Opacity of the highly ionized lanthanides and the effect on the early kilonova [HEAP]

http://arxiv.org/abs/2204.06861


We investigate the effect of the presence of lanthanides (Z = 57- 71) on the kilonova at t~hours after the neutron star merger for the first time. For this purpose, we calculate the atomic structures and the opacities for selected lanthanides: Nd (Z = 60), Sm (Z = 62), and Eu (Z = 63). We consider the ionization degree up to tenth (XI), applicable for the ejecta at t ~ a few hours after the merger, when the temperature is T ~ 10^5 K. We find that the opacities for the highly ionized lanthanides are exceptionally high, reaching k_exp~1000 cm^2/g for Eu, thanks to the energy levels being highly dense. Using the new opacity, we perform radiative transfer simulations to show that the early light curves become fainter by a (maximum) factor of four, in comparison to lanthanide-free ejecta at t~0.1 day. However, the period at which the light curves are affected is relatively brief due to the rapid time evolution of the opacity in the outermost layer of the ejecta. We predict that for a source at a distance of ~100 Mpc, UV brightness for lanthanide-rich ejecta shows a drop to ~21-22 mag at t~0.1 day and the UV peaks around t~0.2 day with a magnitude of ~19 mag. Future detection of such a kilonova by the existing UV satellite like Swift or the upcoming UV satellite ULTRASAT will provide useful constraints on the abundance in the outer ejecta and the corresponding nucleosynthesis conditions in the neutron star mergers.

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S. Banerjee, M. Tanaka, D. Kato, et. al.
Fri, 15 Apr 22
24/50

Comments: 16 pages, 6 figures, submitted to ApJ, comments are welcome

Black holes at cosmic dawn in the redshifted 21cm signal of HI [CEA]

http://arxiv.org/abs/2203.12741


Indirect insights of Pop III stars and Black Holes (BHs) at Cosmic Dawn (CD) may be imprinted as an absorption signal in the 21cm line of HI against the CMB, when the Universe was less than 200 Myr old. To explain the additional large amplitude of the 21cm HI absorption reported by EDGES there have been proposed models based on an additional synchrotron Cosmic Radio Background (CRB) from BH-jet sources that boost the HI absorption signal at CD. The recent observations of radio loud supermassive BHs (SMBHs) in high-z quasars up to z=7 suggest the existence of a CRB from growing BHs at z > 15, of unknown intensity. To match the onset of the EDGES signal a CRB of comparable intensity to that of the CMB is required. Here we provide approximate calculations to analyze this type of absorption signals, taking that of EDGES as an example. Assuming a BH mass to radio luminosity ratio as observed in radio-loud SMBHs of ~10^9 solar masses in quasars at z = 6-7, we find that rapidly growing radio luminous BHs of Intermediate Mass (IMBHs) in their way to become SMBHs, are the only type of astrophysical radio sources of a CRB that could explain the amplitude of the HI absorption reported by EDGES in the interval of z = 18-20. At those redshifts the EDGES signal would imply that the global mass density of IMBHs must be dominant over that of stars, more than 70% of the maximum Stellar Mass Density (SMD) expected at those high redshifts. This suggests that those IMBHs are formed before and grow faster than the bulk of stars, with no large mass contribution from stellar-mass BH remnants of typical Pop III stars. The highly redshifted signals from these IMBHs may be detected at long radio wavelengths with ultrasensitive interferometers such as the SKA, in the infrared with the JWST, and in the X-rays with future space missions.

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I. Mirabel and L. Rodriguez
Fri, 25 Mar 22
42/46

Comments: 34 pages, 2 figures, 1 table. Accepted for publication in New Astronomy Reviews

New Constraints on Exotic Spin-Velocity-Dependent Interactions [CL]

http://arxiv.org/abs/2203.07050


Experimental searches for new, “fifth” forces are attracting a lot of attention because they allow to test theoretical extensions to the standard model. Here, we report a new experimental search for possible fifth forces, specifically spin-and-velocity dependent forces, by using a K-Rb-$^{21}$Ne co-magnetometer and a tungsten ring featuring a high nucleon density. Taking advantage of the high sensitivity of the co-magnetometer, the pseudomagnetic field from the fifth force is measured to be $<7$\,aT. This sets new limits on coupling constants for the neutron-nucleon and proton-nucleon interactions in the range of $\ge 0.1$ m. The coupling constant limits are established to be $|g_V^n|<6.6\times 10^{-11}$ and $|g_V^p|<3.0\times 10^{-10}$, which are more than one order of magnitude tighter than astronomical and cosmological limits on the coupling between the new gauge boson such as Z$’$ and standard model particles.

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K. Wei, W. Ji, C. Fu, et. al.
Tue, 15 Mar 22
81/108

Comments: N/A

Electron-induced excitation, recombination and dissociation of molecular ions initiating the formation of complex organic molecules [CL]

http://arxiv.org/abs/2203.05441


We review the study of dissociative recombination and ro-vibrational excitation of diatomic and small polyatomic molecular ions initiating complex organic molecules formation. In particular, we show how Multichannel Quantum Defect Theory (MQDT) and R-matrix methods are used to compute cross sections and rate coefficients for cations in well defined ro-vibrational levels of the ground electronic state, from sub-meV up to few eV collision energies.
The most recent MQDT results are compared with either other theoretical data, or with measured data obtained in storage-ring experiments.

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J. Mezei, K. Chakrabarti, M. Epée, et. al.
Fri, 11 Mar 22
2/59

Comments: 20 pages, 13 figures

Finite time effects in single and double Compton scattering [CL]

http://arxiv.org/abs/2203.05252


The process of Compton scattering by a free electron with subsequent reemission of one or two photons is considered in the assumption of finite interaction time. The corresponding cross sections are obtained in the framework of relativistic quantum electrodynamics using a modified form of fermion propagator with complex transmitted momentum. It is shown that finite time effects can be observable at sufficiently low energies of scattered photons. The proposed method also regularizes arising infrared divergence in the cross section of the double Compton effect. Possible experimental verification of considered theoretical approach is discussed.

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V. Dubrovich and T. Zalialiutdinov
Fri, 11 Mar 22
16/59

Comments: N/A

Reactive collisions between electrons and BeT$^+$: Complete set of thermal rate coefficients up to 5000 K [CL]

http://arxiv.org/abs/2203.04122


Rate coefficients for the dissociative recombination, vibrational excitation and vibrational de-excitation of the BeT$^{+}$ ion for all vibrational levels of its ground electronic state ($ X\ensuremath{^{1}\Sigma^{+}},v_{i}^{+}=0,\dots,27$) are reported, including in the calculation the contribution of super-excited states of the BeT complex pertaining to three electronic symmetries – $^{2}\Pi$, $^{2}\Sigma^{+}$, and $^{2}\Delta$. These data are suitable for the kinetic modeling of beryllium and tritium containing plasma, as encountered in magnetic fusion devices with beryllium walls (JET, ITER). In the present study we restrict ourselves to incident electron energies from 10$^{-3}$ up to $2.7$ eV, and to electron temperatures between $100$ and $5000$ K, respectively. Together with our earlier and closely related studies on the BeH$^{+}$ and BeD$^{+}$ systems, this present work completes the isotopic coverage for the beryllium monohydride ions. The vibrational energy (rather than the vibrational quantum state) is identified as a proper isotopic similarity parameter, e.g., for reduced but still isotopically correct plasma chemistry models.

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N. Pop, F. Iacob, S. Niyonzima, et. al.
Wed, 9 Mar 22
5/68

Comments: 27 pages, 7 figures, 15 tables

A new benchmark of soft X-ray transition energies of Ne, CO$_2$, and SF$_6$: paving a pathway towards ppm accuracy [IMA]

http://arxiv.org/abs/2203.03725


A key requirement for the correct interpretation of high-resolution X-ray spectra is that transition energies are known with high accuracy and precision. We investigate the K-shell features of Ne, CO$_2$, and SF$_6$ gases, by measuring their photo ion-yield spectra at the BESSY II synchrotron facility simultaneously with the 1s-np fluorescence emission of He-like ions produced in the Polar-X EBIT. Accurate ab initio calculations of transitions in these ions provide the basis of the calibration. While the CO$_2$ result agrees well with previous measurements, the SF$_6$ spectrum appears shifted by ~0.5 eV, about twice the uncertainty of the earlier results. Our result for Ne shows a large departure from earlier results, but may suffer from larger systematic effects than our other measurements. The molecular spectra agree well with our results of time-dependent density functional theory. We find that the statistical uncertainty allows calibrations in the desired range of 1-10 meV, however, systematic contributions still limit the uncertainty to ~40-100 meV, mainly due to the temporal stability of the monochromator energy scale. Combining our absolute calibration technique with a relative energy calibration technique such as photoelectron energy spectroscopy will be necessary to realize its full potential of achieving uncertainties as low as 1-10 meV.

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J. Stierhof, S. Kühn, M. Winter, et. al.
Wed, 9 Mar 22
17/68

Comments: 13 pages, 7 figures

Dissociative recombination of CH$^+$ molecular ion induced by very low energy electrons [IMA]

http://arxiv.org/abs/2203.03484


We used the multichannel quantum defect theory to compute cross sections and rate coefficients for the dissociative recombination of CH$^+$ initially in its lowest vibrational level $v_i^+ = 0$ with electrons of incident energy bellow $0.2$ eV. We have focused on the contribution of the $2$ $^2\Pi$ state which is the main dissociative recombination route at low collision energies. The final cross section is obtained by averaging the relevant initial rotational states $(N_i^+ = 0,\dots,10)$ with a $300$ K Boltzmann distribution.The Maxwell isotropic rate coefficients for dissociative recombination are also calculated for different initial rotational states and for electronic temperatures up to a few hundred Kelvins. Our results are compared to storage-ring measurements.

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J. Mezei, M. Epée, O. Motapon, et. al.
Tue, 8 Mar 22
64/100

Comments: 5 pages, 5 figures

Oscillator-strength ratio of two Fe XVII soft X-ray transitions essential for plasma diagnostics finally agrees with theory [CL]

http://arxiv.org/abs/2201.09070


One of the most enduring and intensively studied problems of X-ray astronomy is the disagreement of state-of-the art theory and observations for the intensity ratio of two ubiquitous Fe{~\sc XVII} transitions of crucial value for plasma diagnostics, dubbed 3C and 3D. We unravel this conundrum at the PETRA~III synchrotron facility by increasing the resolving power two and a half times and the signal-to-noise ratio thousand-fold compared to previous work. Hitherto unnoted Lorentzian wings of 3C, the stronger line, had been indistinguishable from the background. The now-determined experimental oscillator-strength ratio $R= f_{\mathrm{3C}}/f_{\mathrm{3D}}=3.51\pm0.02_{\mathrm{stat}}\pm0.07_{\mathrm{sys}}$ agrees with our present prediction of $R=3.55\pm0.02$, calculated at the largest scale reported for an astrophysical ion. Measured and predicted natural linewidths also mutually agree. Further improvements would allow a test of key QED contributions in this many-electron system.

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S. Kühn, C. Cheung, N. Oreshkina, et. al.
Tue, 25 Jan 22
76/78

Comments: Includes section Supplemental Materials

Cold Atoms in Space: Community Workshop Summary and Proposed Road-Map [IMA]

http://arxiv.org/abs/2201.07789


We summarize the discussions at a virtual Community Workshop on Cold Atoms in Space concerning the status of cold atom technologies, the prospective scientific and societal opportunities offered by their deployment in space, and the developments needed before cold atoms could be operated in space. The cold atom technologies discussed include atomic clocks, quantum gravimeters and accelerometers, and atom interferometers. Prospective applications include metrology, geodesy and measurement of terrestrial mass change due to, e.g., climate change, and fundamental science experiments such as tests of the equivalence principle, searches for dark matter, measurements of gravitational waves and tests of quantum mechanics. We review the current status of cold atom technologies and outline the requirements for their space qualification, including the development paths and the corresponding technical milestones, and identifying possible pathfinder missions to pave the way for missions to exploit the full potential of cold atoms in space. Finally, we present a first draft of a possible road-map for achieving these goals, that we propose for discussion by the interested cold atom, Earth Observation, fundamental physics and other prospective scientific user communities, together with ESA and national space and research funding agencies.

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I. Alonso, C. Alpigiani, B. Altschul, et. al.
Thu, 20 Jan 22
40/77

Comments: Summary of the Community Workshop on Cold Atoms in Space and corresponding Road-map: this https URL

Uncertainties in Atomic Data for Modeling Astrophysical Charge Exchange Plasmas [HEAP]

http://arxiv.org/abs/2201.06146


Relevant uncertainties on theoretical atomic data are vital to determine the accuracy of plasma diagnostics in a number of areas including in particular the astrophysical study. We present a new calculation of the uncertainties on the present theoretical ion-impact charge exchange atomic data and X-ray spectra based on a set of comparisons with the existing laboratory data obtained in historical merged-beam, cold-target recoil-ion momentum spectroscopy, and electron beam ion traps experiments. The average systematic uncertainties are found to be 35-88% on the total cross sections, and 57-75% on the characteristic line ratios. The model deviation increases as the collision energy decreases. The errors on total cross sections further induce a significant uncertainty to the calculation of ionization balance for low temperature collisional plasmas. Substantial improvements of the atomic database and dedicated laboratory measurements are needed to get the current models ready for the X-ray spectra from the next X-ray spectroscopic mission.

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L. Gu, C. Shah and R. Zhang
Wed, 19 Jan 22
103/121

Comments: accepted for publication in Sensors, plasma diagnostics special issue

Improved bounds on ultralight scalar dark matter in the radio-frequency range [CL]

http://arxiv.org/abs/2201.02042


We present a search for fundamental constant oscillations in the range $20$~kHz-$100$ MHz, that may arise within models for ultralight dark matter (UDM). Using two independent, significantly upgraded optical-spectroscopy apparatus, we achieve up to $\times$1000 greater sensitivity in the search relative to previous work. We report no observation of UDM and thus constrain respective couplings to electrons and photons within the investigated UDM particle mass range $8\cdot 10^{-11}-4\cdot 10^{-7}$ eV. The constraints significantly exceed previously set bounds, and as we show, may surpass in future experiments those provided by equivalence-principle experiments in a specific case regarding the combination of UDM couplings probed by the latter.

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O. Tretiak, X. Zhang, N. Figueroa, et. al.
Fri, 7 Jan 22
25/34

Comments: 13 pages, 11 figures

Some features of the direct and inverse double Compton effect as applied to astrophysics [CL]

http://arxiv.org/abs/2112.12991


In the present paper, we consider the process of inverse double Compton (IDC) scattering in the context of astrophysical applications. It is assumed that the two hard X-ray photons emitted from an astrophysical source are scattered on a free electron and converted into a single soft photon of optical range. Using QED S-matrix formalism for the derivation of a cross-section of direct double Compton (DDC) and assuming detailed balance conditions we give an analytical expression for the cross-section of the IDC process. It is shown that at fixed energies of incident photons the inverse cross-section has no infra-red divergences and its behavior is completely defined by the spectral characteristics of the photon source itself, in particular, by the finite interaction time of radiation with an electron. Thus, even for the direct process, the problem of resolving infrared divergence actually refers to a real physical source of radiation in which photons are never actually plane waves. As a result the physical frequency profile of the scattered radiation for direct as well as inverse double Compton processes is a function of both the intensity and line shape of the incident photon field.

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V. Dubrovich and T. Zalialiutdinov
Tue, 28 Dec 21
3/55

Comments: N/A

Some features of the direct and inverse double Compton effect as applied to astrophysics [CL]

http://arxiv.org/abs/2112.12991


In the present paper, we consider the process of inverse double Compton (IDC) scattering in the context of astrophysical applications. It is assumed that the two hard X-ray photons emitted from an astrophysical source are scattered on a free electron and converted into a single soft photon of optical range. Using QED S-matrix formalism for the derivation of a cross-section of direct double Compton (DDC) and assuming detailed balance conditions we give an analytical expression for the cross-section of the IDC process. It is shown that at fixed energies of incident photons the inverse cross-section has no infra-red divergences and its behavior is completely defined by the spectral characteristics of the photon source itself, in particular, by the finite interaction time of radiation with an electron. Thus, even for the direct process, the problem of resolving infrared divergence actually refers to a real physical source of radiation in which photons are never actually plane waves. As a result the physical frequency profile of the scattered radiation for direct as well as inverse double Compton processes is a function of both the intensity and line shape of the incident photon field.

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V. Dubrovich and T. Zalialiutdinov
Tue, 28 Dec 21
19/55

Comments: N/A

Can sub-GeV dark matter coherently scatter on the electrons in the Atom? [CL]

http://arxiv.org/abs/2112.11810


A novel detection of sub-GeV dark matter is proposed in the paper. The electron cloud are boosted by the dark matter and throw away an electron when it is dragged back by the heavy nucleus, namely the coherent scattering of the electron cloud of the atom. The survey in the X-ray diffraction shows that the atomic form factor are much complicate than the naive consideration. The results of the relativistic Hartree-Fock method gives non-trivial shapes of the atom. The detailed calculation of recoil of the electron cloud. The kinetics, the fiducial cross section and the corresponding calculation of detection rate are given analytically. The numerical results show that the limits of the RHF form factor are much stringent than the recoil of a single electron, almost 4 orders stronger. The limits on the RHF form factor are more stringent than the Migdal effect below about several hundred MeV. The physical picture and the corresponding results are promising and need further explorations.

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J. Guo, Y. Sun, W. Wang, et. al.
Thu, 23 Dec 21
30/63

Comments: 12 pages, 8 figures

SpaceQ — Direct Detection of Ultralight Dark Matter with Space Quantum Sensors [CL]

http://arxiv.org/abs/2112.07674


Recent advances in quantum sensors, including atomic clocks, enable searches for a broad range of dark matter candidates. The question of the dark matter distribution in the Solar system critically affects the reach of dark matter direct detection experiments. Partly motivated by the NASA Deep Space Atomic Clock (DSAC), we show that space quantum sensors present new opportunities for ultralight dark matter searches, especially for dark matter states bound to the Sun. We show that space quantum sensors can probe unexplored parameter space of ultralight dark matter, covering theoretical relaxion targets motivated by naturalness and Higgs mixing. If an atomic clock were able to make measurements on the interior of the solar system, it could probe this highly sensitive region directly and set very strong constraints on the existence of such a bound-state halo in our solar system. We present sensitivity projections for space-based probes of ultralight dark matter which couples to electron, photon, and gluon fields, based on current and future atomic, molecular, and nuclear clocks.

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Y. Tsai, J. Eby and M. Safronova
Wed, 22 Dec 21
11/67

Comments: 13 pages, 5 figures

Asteroids for microhertz gravitational-wave detection [CL]

http://arxiv.org/abs/2112.11431


A major challenge for gravitational-wave (GW) detection in the $\mu$Hz band is engineering a test mass (TM) with sufficiently low acceleration noise. We propose a GW detection concept using asteroids located in the inner Solar System as TMs. Our main purpose is to evaluate the acceleration noise of asteroids in the $\mu$Hz band. We show that a wide variety of environmental perturbations are small enough to enable an appropriate class of $\sim 10$ km-diameter asteroids to be employed as TMs. This would allow a sensitive GW detector in the band $\text{(few)} \times 10^{-7} \text{Hz} \lesssim f_{\text{GW}} \lesssim \text{(few)} \times 10^{-5} \text{Hz}$, reaching strain $h_c \sim 10^{-19}$ around $f_{\text{GW}} \sim 10 \mu$Hz, sufficient to detect a wide variety of sources. To exploit these asteroid TMs, human-engineered base stations could be deployed on multiple asteroids, each equipped with an electromagnetic (EM) transmitter/receiver to permit measurement of variations in the distance between them. We discuss a potential conceptual design with two base stations, each with a space-qualified optical atomic clock measuring the round-trip EM pulse travel time via laser ranging. Tradespace exists to optimize multiple aspects of this mission: for example, using a radio-ranging or interferometric link system instead of laser ranging. This motivates future dedicated technical design study. This mission concept holds exceptional promise for accessing this GW frequency band.

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M. Fedderke, P. Graham and S. Rajendran
Wed, 22 Dec 21
36/67

Comments: 50 pages, 9 figures

Measuring the stability of fundamental constants with a network of clocks [CL]

http://arxiv.org/abs/2112.10618


The detection of variations of fundamental constants of the Standard Model would provide us with compelling evidence of new physics, and could lift the veil on the nature of dark matter and dark energy. In this work, we discuss how a network of atomic and molecular clocks can be used to look for such variations with unprecedented sensitivity over a wide range of time scales. This is precisely the goal of the recently launched QSNET project: A network of clocks for measuring the stability of fundamental constants. QSNET will include state-of-the-art atomic clocks, but will also develop next-generation molecular and highly charged ion clocks with enhanced sensitivity to variations of fundamental constants. We describe the technological and scientific aims of QSNET and evaluate its expected performance. We show that in the range of parameters probed by QSNET, either we will discover new physics, or we will impose new constraints on violations of fundamental symmetries and a range of theories beyond the Standard Model, including dark matter and dark energy models.

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G. Barontini, L. Blackburn, V. Boyer, et. al.
Tue, 21 Dec 21
12/86

Comments: N/A

Correspondence between the surface integral and linear combination of atomic orbitals methods for ionic-covalent interactions in mutual neutralisation processes involving H$^-$/D$^-$ [CL]

http://arxiv.org/abs/2112.04991


The surface integral method for estimating ionic-covalent interactions in diatomic systems been successful in producing cross sections for mutual neutralisation (MN) in reasonable agreement with experimental results for branching fractions between final states in systems such as O$^+$/O$^-$ and N$^+$/O$^-$. However, for simpler cases of MN involving H$^-$ or D$^-$, such as Li$^+$/D$^-$ and Na$^+$/D$^-$, it has not produced results that are in agreement with experiments and other theoretical calculations; in particular, for Li$^+$/D$^-$ calculations predict the wrong ordering of importance of final channels, including the incorrect most populated channel. The reason for this anomaly is investigated and a leading constant to the asymptotic H$^-$ wavefunction is found that is different by roughly a factor $1/\sqrt{2}$ to that which has been used in previous calculations with the surface integral method involving H$^-$ or D$^-$. With this correction, far better agreement with both experimental results and with calculations with full quantum and LCAO methods is obtained. Further, it is shown that the surface integral method and LCAO methods have the same asymptotic behaviour, in contrast to previous claims. This result suggests the surface integral method, which is comparatively easy to calculate, has greater potential for estimating MN processes than earlier comparisons had suggested.

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P. Barklem
Fri, 10 Dec 21
83/94

Comments: Accepted by Physical Review A

Comment on ''Quantum sensor networks as exotic field telescopes for multi-messenger astronomy'' [CL]

http://arxiv.org/abs/2111.14351


In the recent work [Dailey et al., Nature Astronomy 5, 150 (2021)], it was claimed that networks of quantum sensors can be used as sensitive multi-messenger probes of astrophysical phenomena that produce intense bursts of relativistic bosonic waves which interact non-gravitationally with ordinary matter. The most promising possibility considered in [Ibid.] involved clock-based searches for quadratic scalar-type interactions, with greatly diminished reach in the case of magnetometer-based searches for derivative-pseudoscalar-type interactions and clock-based searches for linear scalar-type interactions. In this note, we point out that the aforementioned work overlooked the ”back action” of ordinary matter on scalar waves with quadratic interactions and that accounting for back-action effects can drastically affect the detection prospects of clock networks. In particular, back action can cause strong screening of scalar waves near Earth’s surface and by the apparatus itself, rendering clock experiments insensitive to extraterrestrial sources of relativistic scalar waves. Additionally, back-action effects can retard the propagation of scalar waves through the interstellar and intergalactic media, significantly delaying the arrival of scalar waves at Earth compared to their gravitational-wave counterparts and thereby preventing multi-messenger astronomy on human timescales.

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Y. Stadnik
Tue, 30 Nov 21
49/105

Comments: 9 pages, 1 figure

Polarization of fluorescence lines: tracing magnetic field from circumstellar medium to early universe [GA]

http://arxiv.org/abs/2111.09184


Fluorescence emission lines are broadly applied in observation for diffuse medium in the universe. They are normally observed around strong pumping source, tracing the gas in circumstellar medium, reflection nebula, and H\,{\sc ii} regions, etc. They reside in UV/optical and infrared bands and hence could be directly observed with ground-base telescopes. In this letter, we demonstrate the polarization of fluorescence lines as a magnetic field tracer arising from ground state atomic alignment in diffuse medium, including our solar system, supernova remnants (SNRs), as well as quasi-stellar object (QSO) host galaxies. Two types of fluorescence emissions are considered: the primary fluorescence from the excited states; and the secondary fluorescence from the metastable state (forbidden lines). We find that the synergy of these lines could measure three-dimensional magnetic direction: the polarizations of the primary fluorescence lines could reveal the magnetic polar angle along the line-of-sight, whereas the polarization of forbidden lines traces the plane-of-sky magnetic direction. The expected degree of polarization is $P>10\%$. Polarizations of both types of fluorescence emissions have shown strong potential for observations, and are applicable to measure magnetic field within and beyond our galaxy.

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H. Zhang and H. Yan
Thu, 18 Nov 21
55/92

Comments: 11 pages, 6 figures, 2 tables, submitted to ApJ

QSNET, a network of clocks for measuring the stability of fundamental constants [CL]

http://arxiv.org/abs/2110.05944


The QSNET consortium is building a UK network of next-generation atomic and molecular clocks that will achieve unprecedented sensitivity in testing variations of the fine structure constant, $\alpha$, and the electron-to-proton mass ratio, $\mu$. This in turn will provide more stringent constraints on a wide range of fundamental and phenomenological theories beyond the Standard Model and on dark matter models.

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G. Barontini, V. Boyer, X. Calmet, et. al.
Wed, 13 Oct 21
63/80

Comments: N/A

Refined Ultra-Light Scalar Dark Matter Searches with Compact Atom Gradiometers [CEA]

http://arxiv.org/abs/2109.10965


Atom interferometry is a powerful experimental technique that can be employed to search for the oscillation of atomic transition energies induced by ultra-light scalar dark matter (ULDM). Previous studies have focused on the sensitivity to ULDM of km-length atom gradiometers, where atom interferometers are located at the ends of very-long baselines. In this work, we generalise the treatment of the time-dependent signal induced by a linearly-coupled scalar ULDM candidate for vertical atom gradiometers of any length and find correction factors that especially impact the ULDM signal in short-baseline gradiometer configurations. Using these results, we refine the sensitivity estimates for AION-10, a compact 10m gradiometer that will be operated in Oxford, and discuss optimal experimental parameters that enhance the sensitivity to linearly-coupled scalar ULDM. After comparing the sensitivity reach of devices operating in broadband and resonant modes, we show that well-designed compact atom gradiometers are able to explore regions of dark matter parameter space that are not yet constrained.

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L. Badurina, D. Blas and C. McCabe
Fri, 24 Sep 21
65/81

Comments: 14 pages, 5 figures

Signal-to-noise-ratio and SNR-max detection statistics in template bank searches for exotic physics transients with networks of quantum sensors [CEA]

http://arxiv.org/abs/2109.05011


Signal-to-noise ratio (SNR) detection statistic has wide-spread applications. A potential event is recorded when the SNR from a specific template exceeds a threshold set by a desired false positive rate. In template bank searches, the generalization of the SNR statistic is the SNR-max statistic, defined as the maximum of the absolute value of SNRs from individual template matching. While individual SNR realizations are Gaussian distributed, SNR-max probability distribution is non-Gaussian. Moreover, as the individual template-bank SNRs are computed using the same network data streams, SNRs become correlated between templates. Cross-template correlations have sizable effect on the SNR-max probability distribution, and the threshold SNR-max values. Computing threshold SNR-max values for large banks is computationally prohibitive and we develop analytic approaches to computing properties of SNR-max statistic. This is done for nearly orthogonal template banks and for banks with cross-template correlation coefficients “squeezed” about the most probable cross-template correlation value. Since cross-template correlation coefficients quantify similarity of templates, increasing correlations decrease SNR-max thresholds for specific values of false positive rates. Increasing the number of templates in the bank increases the SNR-max thresholds. Our derivations are carried out for networks that may exhibit colored noise and cross-node correlations. Specific applications are illustrated with a dark matter search with atomic clocks and a ”toy” planar network with cyclic rotational symmetry.

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T. Daykin, C. Ellis and A. Derevianko
Mon, 13 Sep 21
48/52

Comments: 27 pages, 13 figures

Lowest order thermal correction to the hydrogen recombination cross section in presence of blackbody radiation [CL]

http://arxiv.org/abs/2108.13079


In the present paper, the correction due to the thermal interaction of two charges to the recombination and ionization processes for the hydrogen atom is considered. The evaluation is based on a rigorous quantum electrodynamic (QED) approach within the framework of perturbation theory. The lowest-order radiative correction to the recombination/ionization cross-section is examined for a wide range of temperatures corresponding to laboratory and astrophysical conditions. The found thermal contribution is discussed both for specific states and for the total recombination and ionization coefficients.

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J. Triaskin, T. Zalialiutdinov, A. Anikin, et. al.
Tue, 31 Aug 21
13/73

Comments: 7 pages, 2 figures, 4 Tables

H, He-like recombination spectra IV; H, He-like recombination spectra IV: clarification and refinement of methodology for $l$-changing collisions [SSA]

http://arxiv.org/abs/2108.09166


Precise spectral diagnostic modelling of H~{\sc i} and He~{\sc ii} recombination spectra can constrain theoretical models which describe many astrophysical environments. Simple analytic expressions are of interest for collisional $l$-changing rate coefficients that are used by large-scale population modelling codes. We review, clarify and improve-upon the modified Pengelly \& Seaton formulae of Guzm\’an \etal We show that the recent poor results for it shown by Vrinceanu \etal are due to their misinterpretation of its usage. We also detail efficient numerical algorithms which should enable the full quantum mechanical expression for such rate coefficients to be used much more routinely by modelling codes. We illustrate with some collisional-radiative population modelling for hydrogen.

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N. Badnell, F. Guzmán, S. Brodie, et. al.
Mon, 23 Aug 21
37/54

Comments: accepted in MNRAS

Depolarization of MgH Solar Lines by Collisions with Hydrogen Atoms [SSA]

http://arxiv.org/abs/2107.11909


Interpretations of the very rich second solar spectrum of the MgH molecule face serious problems owing to the complete lack of any information about rates of collisions between the MgH and hydrogen atoms. This work seeks to begin the process of filling this lacuna by providing, for the first time, quantum excitation, depolarization, and polarization transfer collisional rates of the MgH ground state $X^2\Sigma$. To achieve the goals of this work, potential energy surfaces are calculated and then are included in the Schr\”odinger equation to obtain the probabilities of collisions and, thus, all collisional rates. Our rates are obtained for temperatures ranging from $T !!=$2000 K to $T !!=$15,000 K. Sophisticated genetic programming methods are adopted in order to fit all depolarization rates with useful analytical functions of two variables: the total molecular angular momentum and temperatures. We study the solar implications of our results, and we find that the $X^2\Sigma$ state of MgH is partially depolarized by isotropic collisions with neutral hydrogen in its ground state $^2S$. Our findings show the limits of applicability of the widely used approximation in which the lower-level polarization is neglected.

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S. Qutub, Y. Kalugina and M. Derouich
Tue, 27 Jul 21
68/97

Comments: Published in The Astrophysical Journal

Stochastic Properties of Ultralight Scalar Field Gradients [CEA]

http://arxiv.org/abs/2107.10260


Ultralight axion-like particles are well-motivated dark matter candidates that are the target of numerous direct detection efforts. In the vicinity of the Solar System, such particles can be treated as oscillating scalar fields. The velocity dispersion of the Milky Way determines a coherence time of about 10^6 oscillations, beyond which the amplitude of the axion field fluctuates stochastically. Any analysis of data from an axion direct detection experiment must carefully account for this stochastic behavior to properly interpret the results. This is especially true for experiments sensitive to the gradient of the axion field that are unable to collect data for many coherence times. Indeed, the direction, in addition to the amplitude, of the axion field gradient fluctuates stochastically. We present the first complete stochastic treatment for the gradient of the axion field, including multiple computationally efficient methods for performing likelihood-based data analysis, which can be applied to any axion signal, regardless of coherence time. Additionally, we demonstrate that ignoring the stochastic behavior of the gradient of the axion field can potentially result in failure to discover a true axion signal.

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M. Lisanti, M. Moschella and W. Terrano
Fri, 23 Jul 21
49/63

Comments: 16 pages, figures

The hot circumgalactic medium of the Milky Way: evidence for super-virial, virial, and sub-virial temperature, non-solar chemical composition, and non-thermal line broadening [GA]

http://arxiv.org/abs/2106.13243


For the first time, we present the simultaneous detection and characterization of three distinct phases at $>10^5$ K in $z=0$ absorption, using deep $\it{Chandra}$ observations toward Mrk 421. The extraordinarily high signal-to-noise ratio ($\geqslant60$) of the spectra has allowed us to detect a $\it{hot}$ phase of the Milky Way circumgalactic medium (CGM) at 3.2$^{+1.5}_{-0.5}\times$ 10$^7$ K, coexisting with a $\textit{warm-hot}$ phase at 1.5$\pm$0.1$\times$10$^6$ K and a $\textit{warm}$ phase at 3.0$\pm$0.4$\times$10$^5$ K. The $\textit{warm-hot}$ phase is at the virial temperature of the Galaxy, and the $\textit{warm}$ phase may have cooled from the $\textit{warm-hot}$ phase, but the super-virial $\textit{hot}$ phase remains a mystery. We find that [C/O] in the $\textit{warm}$ and $\textit{warm-hot}$ phases, [Mg/O] in the $\textit{warm-hot}$ phase and [Ne/O] in the $\textit{hot}$ phase are super-solar, and the $\textit{hot}$ and the $\textit{warm-hot}$ phases are $\alpha-$enhanced. Non-thermal line broadening is evident in the $\textit{warm-hot}$ and the $\textit{hot}$ phases and it dominates the total line broadening. Our results indicate that the $>10^5$ K CGM is a complex ecosystem. It provides insights on the thermal and chemical history of the Milky Way CGM, and theories of galaxy evolution.

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S. Das, S. Mathur, A. Gupta, et. al.
Mon, 28 Jun 21
7/51

Comments: 18 pages, 2 tables, 5 figures, 2 appendices (with 1 figure), accepted for publication in ApJ (main)

High-resolution Laboratory Measurements of K-shell X-ray Line Polarization and Excitation Cross Sections in Heliumlike S XV Ions [CL]

http://arxiv.org/abs/2106.06493


We report measurements of electron-impact excitation cross sections for the strong K-shell n=2-1 transitions in S XV using the LLNL EBIT-I electron beam ion trap, two crystal spectrometers, and the EBIT Calorimeter Spectrometer. The cross sections are determined by direct normalization to the well known cross sections of radiative electron capture, measured simultaneously. Using contemporaneous polarization measurements with the two crystal spectrometers, whose dispersion planes are oriented parallel and perpendicular to the electron beam direction, the polarization of the direct excitation line emission is determined, and in turn the isotropic total cross sections are extracted. We further experimentally investigate various line-formation mechanisms, finding that radiative cascades and collisional inner-shell ionization dominate the degree of linear polarization and total line-emission cross sections of the forbidden line $z$.

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C. Shah, N. Hell, A. Hubbard, et. al.
Mon, 14 Jun 21
19/58

Comments: 16 Pages, 9 Figures, published in ApJ

Comprehensive Laboratory Measurements Resolving the LMM Dielectronic Recombination Satellite Lines in Ne-like Fe XVII Ions [CL]

http://arxiv.org/abs/2106.04746


We investigated experimentally and theoretically dielectronic recombination (DR) populating doubly excited configurations $3l3l’$ (LMM) in Fe XVII, the strongest channel for soft X-ray line formation in this ubiquitous species. We used two different electron beam ion traps and two complementary measurement schemes for preparing the Fe XVII samples and evaluating their purity, observing negligible contamination effects. This allowed us to diagnose the electron density in both EBITs. We compared our experimental resonant energies and strengths with those of previous independent work at a storage ring as well as those of configuration interaction, multiconfiguration Dirac-Fock calculations, and many-body perturbation theory. This last approach showed outstanding predictive power in the comparison with the combined independent experimental results. From these we also inferred DR rate coefficients, unveiling discrepancies from those compiled in the OPEN-ADAS and AtomDB databases.

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F. Grilo, C. Shah, S. K”uhn, et. al.
Thu, 10 Jun 21
65/77

Comments: 14 pages, 7 figures, published in ApJ

Collisional effects in the blue wing of Lyman-alpha [SSA]

http://arxiv.org/abs/2106.00766


Spectral observations below Lyman-alpha are now obtained with the Cosmic Origin Spectrograph (COS) on the Hubble Space Telescope (HST). It is therefore necessary to provide an accurate treatment of the blue wing of the Lyman-alpha line that enables correct calculations of radiative transport in DA and DBA white dwarf stars. On the theoretical front, we very recently developed very accurate H-He potential energies for the hydrogen 1s, 2s, and 2p states. Nevertheless, an uncertainty remained about the asymptotic correlation of the Sigma states and the electronic dipole transition moments. A similar difficulty occurred in our first calculations for the resonance broadening of hydrogen perturbed by collisions with neutral H atoms. The aim of this paper is twofold. First, we clarify the question of the asymptotic correlation of the Sigma states, and we show that relativistic contributions, even very tiny, may need to be accounted for a correct long-range and asymptotic description of the states because of the specific 2s 2p Coulomb degeneracy in hydrogen. This effect of relativistic corrections, inducing small splitting of the 2s and 2p states of H, is shown to be important for the Sigma-Sigma$ transition dipole moments in H-He and is also discussed in H-H. Second, we use existent (H-H) and newly determined (H-He) accurate potentials and properties to provide a theoretical investigation of the collisional effects on the blue wing of the Lyman-alpha line of H perturbed by He and H. We study the relative contributions in the blue wing of the H and He atoms according to their relative densities. We finally achieve a comparison with recent COS observations and propose an assignment for a feature centered at 1190 A.

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F. Spiegelman, N. Allard and J. Kielkopf
Thu, 3 Jun 21
41/55

Comments: N/A

Electric quadrupole transitions in carbon dioxide [CL]

http://arxiv.org/abs/2106.00585


Recent advances in the high sensitivity spectroscopy have made it possible, in combination with accurate theoretical predictions, to observe for the first time very weak electric quadrupole transitions in a polar polyatomic molecule of water. Here we present accurate theoretical predictions of the complete quadrupole ro-vibrational spectrum of a non-polar molecule CO$_2$, important in atmospheric and astrophysical applications. Our predictions are validated by recent cavity enhanced absorption spectroscopy measurements and are used to assign few weak features in the recent ExoMars ACS MIR spectroscopic observations of the martian atmosphere. Predicted quadrupole transitions appear in some of the mid-infrared CO$_2$ and water vapor transparency regions, making them important for detection and characterization of the minor absorbers in water- and CO$_2$-rich environments, such as present in the atmospheres of Earth, Venus and Mars.

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A. Yachmenev, A. Campargue, S. Yurchenko, et. al.
Wed, 2 Jun 21
5/48

Comments: N/A

An application of a Si/CdTe Compton camera for the polarization measurement of hard x-rays from highly charged heavy ions [CL]

http://arxiv.org/abs/2105.14236


The methods to measure the polarization of the x-rays from highly charged heavy ions with a significantly higher accuracy than the existing technology is needed to explore relativistic and quantum electrodynamics (QED) effects including the Breit interaction. We developed the Electron Beam Ion Trap Compton Camera (EBIT-CC), a new Compton polarimeter with pixelated multi-layer silicon and cadmium telluride counters. The EBIT-CC detects the three-dimensional position of Compton scattering and photoelectric absorption, and thus the degree of polarization of incoming x-rays can be evaluated. We attached the EBIT-CC on the Tokyo Electron Beam Ion Trap (Tokyo-EBIT) in the University of Electro-Communications. An experiment was performed to evaluate its polarimetric capability through an observation of radiative recombination x-rays emitted from highly charged krypton ions, which were generated by the Tokyo-EBIT. The Compton camera of the EBIT-CC was calibrated for the 75 keV x-rays. We developed event reconstruction and selection procedures and applied them to every registered event. As a result, we successfully obtained the polarization degree with an absolute uncertainty of 0.02. This uncertainty is small enough to probe the difference between the zero-frequency approximation and full-frequency-dependent calculation for the Breit interaction, which is expected for dielectronic recombination x-rays of highly charged heavy ions.

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Y. Tsuzuki, S. Watanabe, S. Oishi, et. al.
Tue, 1 Jun 21
23/72

Comments: 11 pages, 15 figures

Measurement of n-resolved State-Selective Charge Exchange in Ne(8,9)+ Collision with He and H2 [GA]

http://arxiv.org/abs/2105.04438


Charge exchange between highly charged ions and neutral atoms and molecules has been considered as one of the important mechanisms controlling soft X ray emissions in many astrophysical objects and environments. However, for modeling charge exchange soft X ray emission, the data of n and l resolved state selective capture cross sections are often obtained by empirical and semiclassical theory calculations. With a newly built cold target recoil ion momentum spectroscopy (COLTRIMS) apparatus, we perform a series of measurements of the charge exchange of Ne(8,9)+ ions with He and H2 for collision energy ranging from 1 to 24.75 keV/u. n resolved state selective capture cross-sections are reported. By comparing the measured state selective capture cross sections to those calculated by the multichannel Landau Zener method (MCLZ), it is found that MCLZ calculations are in good agreement with the measurement for the dominant n capture for He target. Furthermore, by using nl resolved cross sections calculated by MCLZ and applying l distributions commonly used in the astrophysical literature to experimentally derived n resolved cross sections, we calculate the soft X ray emissions in the charge exchange between 4 keV/u Ne8+ and He by considering the radiative cascade from the excited Ne7+ ions. Reasonable agreement is found in comparison to the measurement for even and separable models, and MCLZ calculations give results in a better agreement.

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J. Xu, C. Xu, R. Zhang, et. al.
Tue, 11 May 21
25/93

Comments: N/A

A quasi-molecular mechanism of formation of hydrogen in the early Universe — a scheme of calculation [CEA]

http://arxiv.org/abs/2104.11584


In our recent papers (Kereslidze et all 2019a, 2021) a non-standard quasi-molecular mechanism was suggested and applied to treat the cosmological recombination. It was assumed that in the pre-recombination stage of evolution of the Universe an electron combined with two neighbouring protons and created the hydrogen molecular ion, $H_2^+$ in highly excited states, which then descended into the lower-lying states or dissociated. In this work, we elaborate the scheme of calculation for free-bound radiative transitions into attractive states of $H_2^+$ as functions of redshift $z$. Together with the earlier developed treatment of bound-bound radiative transitions in $H_2^+$, the elaborated scheme of calculation can be used for the design of a fast and complete cosmological recombination code.

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T. Kereselidze and I. Noselidze
Mon, 26 Apr 21
37/45

Comments: N/A

The number of populated electronic configurations in a hot dense plasma [CL]

http://arxiv.org/abs/2103.07663


In hot dense plasmas of intermediate or high-Z elements in the state of local thermodynamic equilibrium, the number of electronic configurations contributing to key macroscopic quantities such as the spectral opacity and equation of state, can be enormous. In this work we present systematic methods for the analysis of the number of relativistic electronic configurations in a plasma. While the combinatoric number of configurations can be huge even for mid-Z elements, the number of configurations which have non negligible population is much lower and depends strongly and non-trivially on temperature and density. We discuss two useful methods for the estimation of the number of populated configurations: (i) using an exact calculation of the total combinatoric number of configurations within superconfigurations in a converged super-transition-array (STA) calculation, and (ii) by using an estimate for the multidimensional width of the probability distribution for electronic population over bound shells, which is binomial if electron exchange and correlation effects are neglected. These methods are analyzed, and the mechanism which leads to the huge number of populated configurations is discussed in detail. Comprehensive average atom finite temperature density functional theory (DFT) calculations are performed in a wide range of temperature and density for several low, mid and high Z plasmas. The effects of temperature and density on the number of populated configurations are discussed and explained.

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M. Krief
Tue, 16 Mar 21
59/92

Comments: N/A

Electron Impact Excitation of O III: An Assessment [CL]

http://arxiv.org/abs/2103.02581


Tayal and Zatsarinny [Astrophys. J. 850 (2017) 147] have reported results for energy levels, radiative rates (A-values), lifetimes, and effective collision strengths ($\Upsilon$) for transitions among 202 levels of C-like O~III. For the calculations they have adopted the multi-configuration Hartree-Fock (MCHF) code for the energy levels and A-values, and B-spline $R$-matrix (BSR) code for $\Upsilon$. Their reported results cover a (much) larger range of levels/transitions than generally available in the literature, and appear to be accurate for energy levels and A-values. However, the magnitude and behaviour of $\Upsilon$ do not appear to be correct for several transitions. We demonstrate this through our independent calculations by adopting the flexible atomic code (FAC) and recommend a fresh calculation for this important ion.

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K. Aggarwal
Thu, 4 Mar 21
12/83

Comments: 12 pages of text including 11 figures

The influence of photo-induced processes and charge transfer on carbon and oxygen in the lower solar atmosphere [SSA]

http://arxiv.org/abs/2102.09278


To predict line emission in the solar atmosphere requires models which are fundamentally different depending on whether the emission is from the chromosphere or the corona. At some point between the two regions, there must be a change between the two modelling regimes. Recent extensions to the coronal modelling for carbon and oxygen lines in the solar transition region have shown improvements in the emission of singly- and doubly-charged ions, along with Li-like ions. However, discrepancies still remain, particularly for singly-charged ions and intercombination lines. The aim of this work is to explore additional atomic processes that could further alter the charge state distribution and the level populations within ions, in order to resolve some of the discrepancies. To this end, excitation and ionisation caused by both the radiation field and by atom-ion collisions have been included, along with recombination through charge transfer. The modelling is carried out using conditions which would be present in the quiet Sun, which allows an assessment of the part atomic processes play in changing coronal modelling, separately from dynamic and transient events taking place in the plasma. The effect the processes have on the fractional ion populations are presented, as well as the change in level populations brought about by the new excitation mechanisms. Contribution functions of selected lines from low charge states are also shown, to demonstrate the extent to which line emission in the lower atmosphere could be affected by the new modelling.

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R. Dufresne, G. Zanna and N. Badnell
Fri, 19 Feb 21
49/64

Comments: Accepted in MNRAS, 12 pages, 9 figures

One-electron ion in a quantizing magnetic field [CL]

http://arxiv.org/abs/2102.06488


A charged particle in a magnetic field possesses discrete energy levels associated with particle rotation around the field lines. A bound complex of particles with a nonzero net charge possesses an analogous levels associated with its center-of-mass motion and, in addition, the levels associated with internal degrees of freedom, that is with relative motions of its constituent particles. The center-of-mass and internal motions are mutually dependent, which complicates theoretical studies of the binding energies, radiative transitions and other properties of the complex ions moving in quantizing magnetic fields. In this work, we present a detailed derivation of practical expressions for the numerical treatment of such properties of the hydrogenlike ions moving in strong quantizing magnetic fields, which follows and supplements the previous works of Bezchastnov et al. Second, we derive asymptotic analytic expressions for the binding energies, oscillator strengths, and photoionization cross sections of the moving hydrogenlike ions in the limit of an ultra-strong magnetic field.

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I. Demidov and A. Potekhin
Mon, 15 Feb 21
12/53

Comments: 32 pages, 8 figures

Stellar astrophysics in the near UV with VLT-CUBES [IMA]

http://arxiv.org/abs/2102.02205


Alongside future observations with the new European Extremely Large Telescope (ELT), optimised instruments on the 8-10m generation of telescopes will still be competitive at ‘ground UV’ wavelengths (3000-4000 A). The near UV provides a wealth of unique information on the nucleosynthesis of iron-peak elements, molecules, and neutron-capture elements. In the context of development of the near-UV CUBES spectrograph for ESO’s Very Large Telescope (VLT), we are investigating the impact of spectral resolution on the ability to estimate chemical abundances for beryllium and more than 30 iron-peak and heavy elements. From work ahead of the Phase A conceptual design of CUBES, here we present a comparison of the elements observable at the notional resolving power of CUBES (R~20,000) to those with VLT-UVES (R~40,000). For most of the considered lines signal-to-noise is a more critical factor than resolution. We summarise the elements accessible with CUBES, several of which (e.g. Be, Ge, Hf) are now the focus of quantitative simulations as part of the ongoing Phase A study.

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H. Ernandes, C. Evans, B. Barbuy, et. al.
Fri, 5 Feb 21
59/66

Comments: N/A

Simple electron-impact excitation cross-sections including plasma density effects [CL]

http://arxiv.org/abs/2102.00318


The modeling of non-local-thermodynamic-equilibrium plasmas is crucial for many aspects of high-energy-density physics. It often requires collisional-radiative models coupled with radiative-hydrodynamics simulations. Therefore, there is a strong need for fast and as accurate as possible calculations of the cross-sections and rates of the different collisional and radiative processes. We present an analytical approach for the computation of the electron-impact excitation (EIE) cross-sections in the Plane Wave Born (PWB) approximation. The formalism relies on the screened hydrogenic model. The EIE cross-section is expressed in terms of integrals, involving spherical Bessel functions, which can be calculated analytically. In order to remedy the fact that the PWB approximation is not correct at low energy (near threshold), we consider different correcting factors (Elwert-Sommerfeld, Cowan-Robb, Kilcrease-Brookes). We also investigate the role of plasma density effects such as Coulomb screening and quantum degeneracy on the EIE rate. This requires to integrate the collision strength multiplied by the Fermi-Dirac distribution and the Pauli blocking factor. We show that, using an analytical fit often used in collisional-radiative models, the EIE rate can be calculated accurately without any numerical integration, and compare our expression with a correction factor presented in a recent work.

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J. Pain and D. Benredjem
Tue, 2 Feb 21
47/86

Comments: submitted to High Energy Density Phys

Atomic Clocks in Space: A Search for Rubidium and Cesium Masers in M- and L-Dwarfs [SSA]

http://arxiv.org/abs/2101.12298


I searched for the ground state 6.8 and 9.2 GHz hyperfine transitions of rubidium and cesium toward M- and L-dwarfs that show Rb and Cs optical resonance lines. The optical lines can pump the hyperfine transitions, potentially forming masers. These spin-flip transitions of Rb and Cs are the principal transitions used in atomic clocks (the $^{133}$Cs hyperfine transition defines the second). If they are detected in stellar atmospheres, these transitions would provide exceptionally precise clocks that can be used as accelerometers, as exoplanet detectors, as probes of the predictions of general relativity, as probes of light propagation effects, and as a means to do fundamental physics with telescopes. Observations of 21 M- and L-dwarfs, however, show no evidence for Rb or Cs maser action, and a previous survey of giant stars made no Rb maser detections.

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J. Darling
Mon, 1 Feb 21
68/69

Comments: 3 pages, 1 table. Accepted by RNAAS

Constraints on the Coupling between Axionlike Dark Matter and Photons Using an Antiproton Superconducting Tuned Detection Circuit in a Cryogenic Penning Trap [CEA]

http://arxiv.org/abs/2101.11290


We constrain the coupling between axionlike particles (ALPs) and photons, measured with the superconducting resonant detection circuit of a cryogenic Penning trap. By searching the noise spectrum of our fixed-frequency resonant circuit for peaks caused by dark matter ALPs converting into photons in the strong magnetic field of the Penning-trap magnet, we are able to constrain the coupling of ALPs with masses around $2.7906-2.7914\,\textrm{neV/c}^2$ to $g_{a\gamma}< 1 \times 10^{-11}\,\textrm{GeV}^{-1}$. This is more than one order of magnitude lower than the best laboratory haloscope and approximately 5 times lower than the CERN axion solar telescope (CAST), setting limits in a mass and coupling range which is not constrained by astrophysical observations. Our approach can be extended to many other Penning-trap experiments and has the potential to provide broad limits in the low ALP mass range.

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J. Devlin, M. Borchert, S. Erlewein, et. al.
Thu, 28 Jan 21
52/64

Comments: 7 pages, 3 figures

Extended theoretical transition data in C I – IV [CL]

http://arxiv.org/abs/2101.09114


Accurate atomic data are essential for opacity calculations and for abundance analyses of the Sun and other stars. The aim of this work is to provide accurate and extensive results of energy levels and transition data for C I – IV. The Multiconfiguration Dirac-Hartree-Fock and relativistic configuration interaction methods were used in the present work. To improve the quality of the wave functions and reduce the relative differences between length and velocity forms for transition data involving high Rydberg states, alternative computational strategies were employed by imposing restrictions on the electron substitutions when constructing the orbital basis for each atom and ion. Transition data, e.g., weighted oscillator strengths and transition probabilities, are given for radiative electric dipole (E1) transitions involving levels up to 1s$^2$2s$^2$2p6s for C I, up to 1s$^2$2s$^2$7f for C II, up to 1s$^2$2s7f for C III, and up to 1s$^2$8g for CIV. Using the difference between the transition rates in length and velocity gauges as an internal validation, the average uncertainties of all presented E1 transitions are estimated to be 8.05%, 7.20%, 1.77%, and 0.28%, respectively, for C I – IV. Extensive comparisons with available experimental and theoretical results are performed and good agreement is observed for most of the transitions. In addition, the C I data were employed in a reanalysis of the solar carbon abundance. The new transition data give a line-by-line dispersion similar to the one obtained when using transition data that are typically used in stellar spectroscopic applications today.

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W. Li, A. Amarsi, A. Papoulia, et. al.
Mon, 25 Jan 21
1/60

Comments: 21 pages, 4 figures

Measurement of Absolute Single and Double Electron Capture Cross Sections for O6+ Ions Collision with CO2, CH4, H2 and N2 [CL]

http://arxiv.org/abs/2101.09074


The absolute electron capture cross sections for single and double charge exchanges between the highly charged ions O6+ and CO2, CH4, H2, N2, the dominant collision processes in the solar wind, have been measured in the energy from 7 keVq (2.63 keV/u) to 52 keVq (19.5 keV/u). These measurements were carried out in the new experimental instrument set up at Fudan University, and the error of cross sections for single and double charge exchanges at the 1{\sigma} confidence level are about 11% and 16%, respectively. Limited agreement is achieved with single electron capture results calculated by the classical over-barrier model. These cross sections data are useful for simulation ion-neutral processes in astrophysical environments and to improve the present theoretical model of fundamental atomic processes.

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J. Han, L. Wei, B. Wang, et. al.
Mon, 25 Jan 21
4/60

Comments: 9 pages, 4 pages

Mutual neutralisation in Li$^+$+H$^-$/D$^-$ and Na$^+$+H$^-$/D$^-$ collisions: Implications of experimental results for non-LTE modelling of stellar spectra [SSA]

http://arxiv.org/abs/2012.11968


Advances in merged-beams instruments have allowed experimental studies of the mutual neutralisation (MN) processes in collisions of both Li$^+$ and Na$^+$ ions with D$^-$ at energies below 1 eV. These experimental results place constraints on theoretical predictions of MN processes of Li$^+$ and Na$^+$ with H$^-$, important for non-LTE modelling of Li and Na spectra in late-type stars. We compare experimental results with calculations for methods typically used to calculate MN processes, namely the full quantum (FQ) approach, and asymptotic model approaches based on the linear combination of atomic orbitals (LCAO) and semi-empirical (SE) methods for deriving couplings. It is found that FQ calculations compare best overall with the experiments, followed by the LCAO, and the SE approaches. The experimental results together with the theoretical calculations, allow us to investigate the effects on modelled spectra and derived abundances and their uncertainties arising from uncertainties in the MN rates. Numerical experiments in a large grid of 1D model atmospheres, and a smaller set of 3D models, indicate that neglect of MN can lead to abundance errors of up to 0.1 dex (26\%) for Li at low metallicity, and 0.2 dex (58\%) for Na at high metallicity, while the uncertainties in the relevant MN rates as constrained by experiments correspond to uncertainties in abundances of much less than 0.01~dex (2\%). This agreement for simple atoms gives confidence in the FQ, LCAO and SE model approaches to be able to predict MN with the accuracy required for non-LTE modelling in stellar atmospheres.

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P. Barklem, A. Amarsi, J. Grumer, et. al.
Wed, 23 Dec 20
28/72

Comments: Accepted by ApJ

Reference wavelengths of Si II, C II, Fe I, and Ni II [IMA]

http://arxiv.org/abs/2012.11476


Wavelengths of absorption lines in the spectra of galaxies along the line-of-sight to distant quasars can be used to probe the variablility of the fine structure constant, $\alpha$, at high redshifts, provided that the laboratory wavelengths are known to better than 6 parts in 10$^8$, corresponding to a radial velocity of $\approx$~20 ms$^{-1}$. For several lines of Si II, C II, Fe I, and Ni II, previously published wavelengths are inadequate for this purpose. Improved wavelengths for these lines were derived by re-analyzing archival Fourier transform (FT) spectra of iron hollow cathode lamps (HCL) and a silicon carbide Penning discharge lamp, and with new spectra of nickel HCLs. By re-optimizing the energy levels of Fe I, the absolute uncertainty of 13 resonance lines has been reduced by over a factor of 2. A similar analysis for Si II gives improved values for 45 lines with wavelength uncertainties over an order of magnitude smaller than previous measurements. Improved wavelengths for 8 lines of Ni II were measured and Ritz wavelengths from optimized energy levels determined for an additional 3 lines at shorter wavelengths. Three lines of C II near 135~nm were observed using FT spectroscopy and the wavelengths confirm previous measurements.

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G. Nave and C. Clear
Tue, 22 Dec 20
57/89

Comments: 7 pages, 4 figures. This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review

Atomic transitions for adaptive optics [IMA]

http://arxiv.org/abs/2012.10256


This paper reviews atoms and ions in the upper atmosphere, including the mesospheric metals Na, Fe, Mg$^+$, Si$^+$, Ca$^+$, K and also non-metallic species N, N$^+$, O, H, considering their potential for astronomical adaptive optics. Na and Fe are the best candidates for the creation of polychromatic laser guide stars, with the strongest returns coming from transitions that can be reached by excitation at two wavelengths. Ca$^+$ and Si$^+$ have strong visible-light transitions, but require short wavelengths, beyond the atmospheric cutoff, for excitation from the ground state. Atomic O, N and N$^+$ have strong transitions and high abundances in the mesosphere. The product of column density and cross section for these species can be as high as $10^5$ for O and several hundred for N and N$^+$, making them potential candidates for amplified spontaneous emission. However they require vacuum-ultraviolet wavelengths for excitation.

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R. Yang, J. Hellemeier and P. Hickson
Mon, 21 Dec 20
61/75

Comments: 18 pages, 8 figures

A Kinetic Study of the N(2D) + C2H4 Reaction at Low Temperature [CL]

http://arxiv.org/abs/2012.00655


Electronically excited nitrogen atoms N(2D) are important species in the photochemistry of N2 based planetary atmospheres such as Titan. Despite this, few N(2D) reactions have been studied over the appropriate low temperature range. During the present work, rate constants were measured for the N(2D) + ethene (C2H4) reaction using a supersonic flow reactor at temperatures between 50 K and 296 K. Here, a chemical reaction was used to generate N(2D) atoms, which were detected directly by laser induced fluorescence in the vacuum ultraviolet wavelength region. The measured rate constants displayed very little variation as a function of temperature, with substantially larger values than those obtained in previous work. Indeed, considering an average temperature of 170 K for the atmosphere of Titan leads to a rate constant that is almost seven times larger than the currently recommended value. In parallel, electronic structure calculations were performed to provide insight into the reactive process. While earlier theoretical work at a lower level predicted the presence of a barrier for the N(2D) + C2H4 reaction, the present calculations demonstrate that two of the five doublet potential energy surfaces correlating with reagents are likely to be attractive, presenting no barriers for the perpendicular approach of the N atom to the carbon double bond of ethene. The measured rate constants and new product channels taken from recent dynamical investigations of this process are included in a 1D coupled ion-neutral model of Titans atmosphere. These simulations indicate that the modeled abundances of numerous nitrogen bearing compounds are noticeably affected by these changes.

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K. Hickson, C. Bray, J. Loison, et. al.
Wed, 2 Dec 20
10/71

Comments: 21 pages, 5 figures, 2 tables

Two-body neutral Coulomb system in a magnetic field at rest: from Hydrogen atom to positronium [CL]

http://arxiv.org/abs/2012.00044


A simple uniform approximation for the nodeless wavefunction is constructed for a {\it neutral} system of two Coulomb charges of different masses $(-q,m_1)$ and $(q,m_2)$ at rest in a constant uniform magnetic field for the states of positive and negative parity, ${(1s_0)}$ and ${(2p_0)}$, respectively. It is shown that by keeping the mass and charge of one of the bodies fixed, all systems with different second body masses are related. This allows one to consider the second body as infinitely-massive and to take such a system as basic. Three physical systems are considered in details: the Hydrogen atom with (in)-finitely massive proton (deuteron, triton) and the positronium atom $(-e,e)$. We derive the Riccati-Bloch and Generalized-Bloch equations, which describe the domains of small and large distances, respectively. Based on the interpolation of the small and large distance behavior of the logarithm of the wavefunction, a compact 10-parametric function is proposed. Taken as a variational trial function it provides accuracy of not less than 6 significant digits (s.d.) ($\lesssim 10^{-6}$ in relative deviation) for the total energy in the whole domain of considered magnetic fields $[0\,,\,10^4]$ a.u. and not less than 3 s.d. for the quadrupole moment $Q_{zz}$. In order to get reference points the Lagrange Mesh Method with 16K mesh points was used to get from 10 to 6 s.d. in energy from small to large magnetic fields. Based on the Riccati-Bloch equation the first 100 perturbative coefficients for the energy, in the form of rational numbers, are calculated and, using the Pad\’e-Borel re-summation procedure, the energy is found with not less than 10 s.d. at magnetic fields $\leq 1$\,a.u.

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J. Valle, A. Turbiner and A. Ruiz
Wed, 2 Dec 20
51/71

Comments: 47 pages, 7 tables, 5 figures, 3 appendices

Rydberg States of H$_3$ and HeH as Potential Coolants for Primordial Star Formation [CL]

http://arxiv.org/abs/2011.05250


Current theory and measurements establish the age of the universe as ca. 13.8 billion years. For the first several hundred million years of its existence, it was a dark, opaque void. After that, the hydrogen atoms comprising most of the “ordinary” matter began to condense and ionize, eventually forming the first stars that would illuminate the sky. Details of how these “primordial” stars formed have been widely debated, but remain elusive. A central issue in this process is the mechanism by which the primordial gas (mainly hydrogen and helium atoms) collected via the action of dark matter cools and further accretes to fusion densities. Current models invoke collisional excitation of H$_2$ molecular rotations and subsequent radiative rotational transitions allowed by the weak molecular quadrupole moment. In this article, we review the salient considerations, and present some new ideas, bases on recent spectroscopic observations of neutral H$_3$ Rydberg electronic state emission in the mid-infrared.

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G. Kannan, J. Chien, A. Benjamin, et. al.
Wed, 11 Nov 20
68/69

Comments: N/A

Robust laboratory limits on a cosmological spatial gradient in the electromagnetic fine-structure constant from accelerometer experiments [CL]

http://arxiv.org/abs/2010.01798


Quasar absorption spectral data indicate the presence of a spatial gradient in the electromagnetic fine-structure constant $\alpha$ on cosmological length scales. We point out that experiments with accelerometers, including torsion pendula and atom interferometers, can be used as sensitive probes of cosmological spatial gradients in the fundamental constants of nature, which give rise to equivalence-principle-violating forces on test masses. Using laboratory data from the Eöt-Wash experiment, we constrain spatial gradients in $\alpha$ along any direction to be $|\mathbf{\nabla} \alpha / \alpha| < 6.6 \times 10^{-4}~(\textrm{Glyr})^{-1}$ at $95\%$ confidence level. Our result represents an order of magnitude improvement over laboratory bounds from clock-based searches for a spatial gradient in $\alpha$ directed along the observed cosmological $\alpha$-dipole axis.

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Y. Stadnik
Tue, 6 Oct 2020
27/85

Comments: 7 pages

Atomic Data Assessment with PyNeb [GA]

http://arxiv.org/abs/2009.10586


PyNeb is a Python package widely used to model emission lines in gaseous nebulae. We take advantage of its object-oriented architecture, class methods, and historical atomic database to structure a practical environment for atomic data assessment. Our aim is to reduce the uncertainties in parameter space (line-ratio diagnostics, electron density and temperature, and ionic abundances) arising from the underlying atomic data by critically selecting the PyNeb default datasets. We evaluate the questioned radiative-rate accuracy of the collisionally excited forbidden lines of the N- and P-like ions (O II, Ne IV, S II, Cl III, and Ar IV), which are used as density diagnostics. With the aid of observed line ratios in the dense NGC 7027 planetary nebula and careful data analysis, we arrive at emissivity-ratio uncertainties from the radiative rates within 10\%, a considerable improvement over a previously predicted 50\%. We also examine the accuracy of an extensive dataset of electron-impact effective collision strengths for the carbon isoelectronic sequence recently published. By estimating the impact of the new data on the pivotal temperature diagnostics of [N II] and [O III] and by benchmarking the collision strength with a measured resonance position, we question their usefulness in nebular modeling. We confirm that the effective-collision-strength scatter of selected datasets for these two ions does not lead to uncertainties in the temperature diagnostics larger than 10\%.

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C. Morisset, V. Luridiana, J. García-Rojas, et. al.
Wed, 23 Sep 20
-1720/86

Comments: Accepted for publication in Atoms MDPI

Computational insight into diatomic molecules as probes to measure the variation of the proton-to-electron mass ratio [CL]

http://arxiv.org/abs/2008.10799


Astrophysical molecular spectroscopy is an important means of searching for new physics through probing the variation of the proton-to-electron mass ratio, $\mu$. New molecular probes could provide tighter constraints on the variation of $\mu$ and better direction for theories of new physics. Here we summarise our previous paper \citep{19SyMoCu.CN} for astronomers, highlighting the importance of accurate estimates of peak molecular abundance and temperature as well as spectral resolution and sensitivity of telescopes in different regions of the electromagnetic spectrum. Whilst none of the 11 astrophysical diatomic molecules we investigated showed enhanced sensitive rovibronic transitions at observable intensities for astrophysical environments, we have gained a better understanding of the factors that contribute to high sensitivities. From our results, CN, CP, SiN and SiC have shown the most promise of all astrophysical diatomic molecules for further investigation, with further work currently being done on CN.

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A. Syme and L. McKemmish
Wed, 26 Aug 20
-1201/66

Comments: N/A

Precision Metrology Meets Cosmology: Improved Constraints on Ultralight Dark Matter from Atom-Cavity Frequency Comparisons [CL]

http://arxiv.org/abs/2008.08773


We conduct frequency comparisons between a state-of-the-art strontium optical lattice clock, a cryogenic crystalline silicon cavity, and a hydrogen maser to set new bounds on the coupling of ultralight dark matter to Standard Model particles and fields in the mass range of $10^{-16}$ $-$ $10^{-21}$ eV. The key advantage of this two-part ratio comparison is the differential sensitivities to time variation of both the fine-structure constant and the electron mass, achieving a substantially improved limit on the moduli of ultralight dark matter, particularly at higher masses than typical atomic spectroscopic results. Furthermore, we demonstrate an extension of the search range to even higher masses by use of dynamical decoupling techniques. These results highlight the importance of using the best performing atomic clocks for fundamental physics applications as all-optical timescales are increasingly integrated with, and will eventually supplant, existing microwave timescales.

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C. Kennedy, E. Oelker, J. Robinson, et. al.
Fri, 21 Aug 20
-1129/51

Comments: 11 pages, 10 figures

Photoionization of astrophysically relevant atomic ions at PIPE [CL]

http://arxiv.org/abs/2008.05264


We review recent work on the photoionization of atomic ions of astrophysical interest that has been carried out at the photon-ion merged-beams setup PIPE, a permanently installed end station at the XUV beamline P04 of the PETRAIII synchrotron radiation source operated by DESY in Hamburg, Germany. Our results on single and multiple L-shell photoionization of Fe+, Fe2+, and Fe3+ ions and on single and multiple K-shell photoionization of C-, C+, C4+, Ne+, and Si2+ ions are discussed in astrophysical contexts. Moreover, these experimental results bear witness of the fact, that the implementation of the photon-ion merged-beams method at one of the world’s brightest synchrotron light sources has led to a breakthrough for the experimental study of atomic inner-shell photoionization processes with ions.

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S. Schippers and A. Müller
Thu, 13 Aug 20
-915/67

Comments: 18 pages, 7 figures, 1 table, 113 references

The influence of the electric polarization of hydrogen atoms on the red shift of its spectral lines [GA]

http://arxiv.org/abs/2008.02645


The Lorentz oscillator system is studied to interpret the spectral lines of hydrogen atoms. The dielectric constant of this system is analyzed, which takes into account the electrical polarization of hydrogen atoms. This dielectric constant gives the red shift of the spectral line and the appearance of the optical spectrum dip. This dip is on the blue side of the spectral position of the shifted line. The value of this red shift and the width of this dip strongly depend on the hydrogen atom concentration and the spectral position of the not shifted line. This red shift increases with an increase in the hydrogen atom concentration.

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V. Severin
Fri, 7 Aug 20
-736/46

Comments: 11 pages, 3 figures

X-ray spectra of the Fe-L complex II: atomic data constraints from EBIT experiment and X-ray grating observations of Capella [HEAP]

http://arxiv.org/abs/2007.03843


The Hitomi results for the Perseus cluster have shown that accurate atomic models are essential to the success of X-ray spectroscopic missions, and just as important as knowledge on instrumental calibration and astrophysical modeling. Preparing the models requires a multifaceted approach, including theoretical calculations, laboratory measurements, and calibration using real observations. In a previous paper, we presented a calculation of the electron impact cross sections on the transitions forming the Fe-L complex. In the present work, we systematically test the calculation against cross sections of ions measured in an electron beam ion trap experiment. A two-dimensional analysis in the electron beam energies and X-ray photon energies is utilized to disentangle radiative channels following dielectronic recombination, direct electron-impact excitation, and resonant excitation processes in the experimental data. The data calibrated through laboratory measurements are further fed into global modeling of the Chandra grating spectrum of Capella. We investigate and compare the fit quality, as well as sensitivity of the derived physical parameters to the underlying atomic data and the astrophysical plasma modeling. We further list the potential areas of disagreement between the observation and the present calculations, which in turn calls for renewed efforts in theoretical calculations and targeted laboratory measurements.

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L. Gu, C. Shah, J. Mao, et. al.
Thu, 9 Jul 20
-7/70

Comments: Accepted for publication in A&A

Effects of density on the oxygen ionisation equilibrium in collisional plasmas [SSA]

http://arxiv.org/abs/2007.00465


The ion populations most frequently adopted for diagnostics in collisional plasmas are derived from the density independent, coronal approximation. In higher density, lower temperature conditions, ionisation rates are enhanced once metastable levels become populated, and recombination rates are suppressed if ions recombine into Rydberg levels. As a result, the formation temperatures of ions shift, altering the diagnostics of the plasma. To accurately model the effect of ionisation from metastable levels, new electron impact, ionisation cross sections have been calculated for oxygen, both for direct ionisation and excitation–auto-ionisation of the ground and metastable levels. The results have been incorporated into collisional radiative modelling to show how the ionisation equilibrium of oxygen changes once metastable levels become populated. Suppression of dielectronic recombination has been estimated and also included in the modelling, demonstrating the shifts with density in comparison to the coronal approximation. The final results for the ionisation equilibrium are used in differential emission measure modelling to predict line intensities for many lines emitted by O II-VI in the solar transition region. The predictions show improved agreement by 15-40% for O II, O VI and the inter-combination lines of O III-V, when compared to results from coronal approximation modelling. While there are still discrepancies with observations of these lines, this could, to a large part, be explained by variability in the observations.

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R. Dufresne, G. Zanna and N. N.R.Badnell
Thu, 2 Jul 20
26/64

Comments: 15 pages, 11 figures, accepted by MNRAS

New bounds on macroscopic scalar-field topological defects from non-transient signatures due to environmental dependence and spatial variations of the fundamental constants [CL]

http://arxiv.org/abs/2006.00185


We point out that in models of macroscopic topological defects composed of one or more scalar fields that interact with standard-model fields via scalar-type couplings, the back-action of ambient matter on the scalar field(s) produces an environmental dependence of the fundamental constants of nature, as well as spatial variations of the fundamental constants in the vicinity of dense bodies such as Earth. In sufficiently dense environments, spontaneous symmetry breaking may be inhibited altogether for $\phi^2$ interactions, potentially delaying the cosmological production of topological defects. We derive bounds on non-transient variations of the fundamental constants from torsion-pendulum experiments that search for equivalence-principle-violating forces, experiments comparing the frequencies of ground- and space-based atomic clocks, as well as ground-based clocks at different heights in the recent Tokyo Skytree experiment, and measurements comparing atomic and molecular transition frequencies in terrestrial and low-density astrophysical environments. Our results constrain the present-day mass-energy fraction of the Universe due to a network of infinite domain walls produced shortly after the BBN or CMB epochs to be $\Omega_{\textrm{walls},0} \ll 10^{-10}$ for the symmetron model with a $\phi^4$ potential and $\phi^2$ interactions, improving over CMB quadrupolar temperature anisotropy bounds by at least 5 orders of magnitude. Our newly derived bounds on domain walls with $\phi^2$ interactions via their effects of non-transient variations of the fundamental constants are significantly more stringent than previously reported clock- and cavity-based limits on passing domain walls via transient signatures and previous bounds from different types of non-transient signatures, under the same set of assumptions.

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Y. Stadnik
Tue, 2 Jun 20
15/90

Comments: 37 pages, 6 figures

Direct limits on the interaction of antiprotons with axion-like dark matter [CL]

http://arxiv.org/abs/2006.00255


Astrophysical observations indicate that there is roughly five times more dark matter in the Universe than ordinary baryonic matter, with an even larger amount of the Universe’s energy content due to dark energy. So far, the microscopic properties of these dark components have remained shrouded in mystery. In addition, even the five percent of ordinary matter in our Universe has yet to be understood, since the Standard Model of particle physics lacks any consistent explanation for the predominance of matter over antimatter. Inspired by these central problems of modern physics, we present here a direct search for interactions of antimatter with dark matter, and place direct constraints on the interaction of ultra-light axion-like particles $-$ one of the dark-matter candidates $-$ and antiprotons. If antiprotons exhibit a stronger coupling to these dark-matter particles than protons, such a CPT-odd coupling could provide a link between dark matter and the baryon asymmetry in the Universe. We analyse spin-flip resonance data acquired with a single antiproton in a Penning trap [Smorra et al., Nature 550, 371 (2017)] in the frequency domain to search for spin-precession effects from ultra-light axions with a characteristic frequency governed by the mass of the underlying particle. Our analysis constrains the axion-antiproton interaction parameter $f_a/C_{\overline{p}}$ to values greater than $0.1$ to $0.6$ GeV in the mass range from $2 \times 10^{-23}$ to $4 \times 10^{-17}\,$eV/$c^2$, improving over astrophysical antiproton bounds by up to five orders of magnitude. In addition, we derive limits on six combinations of previously unconstrained Lorentz-violating and CPT-violating terms of the non-minimal Standard Model Extension.

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C. Smorra, Y. Stadnik, P. Blessing, et. al.
Tue, 2 Jun 20
20/90

Comments: 26 pages, 7 figures, including supplementary information

MARVEL analysis of the measured high-resolution rovibronic spectra of the calcium monohydroxide radical (CaOH) [CL]

http://arxiv.org/abs/2005.14194


The calcium monohydroxide radical (CaOH) is an important astrophysical molecule relevant to cool stars and rocky exoplanets, amongst other astronomical environments. Here, we present a consistent set of highly accurate rovibronic (rotation-vibration-electronic) energy levels for the five lowest electronic states ($\tilde{X}\,^2\Sigma^+$, $\tilde{A}\,^2\Pi$, $\tilde{B}\,^2\Sigma^+$, $\tilde{C}\,^2\Delta$, $\tilde{D}\,^2\Sigma^+$) of CaOH. A comprehensive analysis of the published spectroscopic literature on this system has allowed 1955 energy levels to be determined from 3204 rovibronic experimental transitions, all with unique quantum number labelling and measurement uncertainties. The dataset covers rotational excitation up to $J=62.5$ for molecular states below 29\,000~cm$^{-1}$. The analysis was performed using the MARVEL algorithm, which is a robust procedure based on the theory of spectroscopic networks. The dataset provided will significantly aid future interstellar, circumstellar and atmospheric detections of CaOH, as well as assisting in the design of efficient laser cooling schemes in ultracold molecule research and precision tests of fundamental physics.

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Y. Wang, A. Owens, J. Tennyson, et. al.
Mon, 1 Jun 20
15/50

Comments: N/A

Photodetachment of the outer-most electrons in a few- and many-electron atomic systems [CL]

http://arxiv.org/abs/2005.03122


Photodetachment of the outer-most electrons in few- and many-electron atomic systems is studied in the non-relativistic dipole approximation. Such a photodetachment is analyzed for the neutral atoms and positively charged atomic ions. We also investigate photodetachment of the outer-most electrons in the negatively charged atomic ions, including the negatively charged hydrogen ion. In all these cases we have derived the closed analytical formulas for the photodetachemnt cross-section(s) of the outer-most electrons.

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A. Frolov
Fri, 8 May 20
24/72

Comments: N/A

Opacity modelling of heavy-metal hot subdwarfs. Photoionization of Sr$^0$, Y$^{+}$ and Zr$^{2+}$ [CL]

http://arxiv.org/abs/2004.13589


Heavy-metal hot subdwarfs (sdB and sdO) represent a small group of stars with unusually high concentrations of trans-iron elements in their atmospheres, having abundances ~ 10000 times solar. One example is LS IV-14$^{\circ}$ 116, where a number of heavy-metal absorption lines of Sr II, Y III and Zr IV have been observed in the optical band 4000 – 5000 A. We use a fully relativistic Dirac atomic R-Matrix (DARC) to calculate photoionization cross sections of Sr$^{0}$, Y$^{+}$ and Zr$^{2+}$ from their ground state to the twentieth excited level. We use the cross sections and the oscillator strengths to simulate the spectrum of a hot subdwarf. We obtain complete sets of photoionization cross sections for the three ions under study. We use these data to calculate the opacity of the stellar atmospheres of hot subdwarf stars, and show that for overabundances observed in some heavy-metal subdwarves, photo-excitation from zirconium, in particular, does contribute some back warming in the model.

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L. Fernández-Menchero, C. Jeffery, C. Ramsbottom, et. al.
Wed, 29 Apr 20
40/75

Comments: 8 pages, 6 figures, 6 tables

Stellar laboratories. X. New Cu IV – VII oscillator strengths and the first detection of copper and indium in hot white dwarfs [SSA]

http://arxiv.org/abs/2004.01633


Accurate atomic data is an essential ingredient for the calculation of reliable non-local thermodynamic equilibrium (NLTE) model atmospheres that are mandatory for the spectral analysis of hot stars. We aim to search for and identify for the first time spectral lines of copper (atomic number Z = 29) and indium (Z = 49) in hot white dwarf (WD) stars and to subsequently determine their photospheric abundances. Oscillator strengths of Cu IV – VII were calculated to include radiative and collisional bound-bound transitions of Cu in our NLTE model-atmosphere calculations. Oscillator strengths of In IV – VI were compiled from the literature. We newly identified 1 Cu IV, 51 Cu V, 2 Cu VI, and 5 In Vlines in the ultraviolet (UV) spectrum of DO-type WD RE 0503-289. We determined the photospheric abundances of 9.3 X 10-5 (mass fraction, 132 times solar) and 3.0 X 10-5 (56 600 times solar), respectively; we also found Cu overabundances in the DA-type WD G191-B2B (6.3 X 10**-6, 9 times solar). All identified Cu IV – VI lines in the UV spectrum of RE 0503-289 were simultaneously well reproduced with our newly calculated oscillator strengths. With the detection of Cu and In in RE 0503-289, the total number of trans-iron elements (Z > 28) in this extraordinary WD reaches an unprecedented number of 18.

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T. Rauch, S. Gamrath, P. Quinet, et. al.
Mon, 6 Apr 20
41/46

Comments: 32 pages, 7 figures

High-Precision Determination of Oxygen-K$α$ Transition Energy Excludes Incongruent Motion of Interstellar Oxygen [CL]

http://arxiv.org/abs/2003.13838


We demonstrate a widely applicable technique to absolutely calibrate the energy scale of x-ray spectra with experimentally well-known and accurately calculable transitions of highly charged ions, allowing us to measure the K-shell Rydberg spectrum of molecular O$_2$ with 6 meV uncertainty. We reveal a systematic $\sim$450 meV shift from previous literature values, and settle an extraordinary discrepancy between astrophysical and laboratory measurements of neutral atomic oxygen, the latter being calibrated against the aforementioned O$_2$ literature values. Because of the widespread use of such, now deprecated, references, our method impacts on many branches of x-ray absorption spectroscopy. Moreover, it potentially reduces absolute uncertainties there to below the meV level.

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M. Leutenegger, S. Kühn, P. Micke, et. al.
Wed, 1 Apr 20
4/83

Comments: Submitted to PRL. 7 pages, 3 figures