http://arxiv.org/abs/1803.09035
Astrochemical evolution step of polycyclic aromatic hydrocarbon (PAH) around a Herbig Ae young star was analyzed using the first principles quantum chemical calculation. For simplicity, model molecule was selected to be acenaphthylene (C12H8) with hydrocarbon one pentagon combined with two hexagons. In a protoplanetary disk, molecules are illuminated by high energy photon from the central star and ionized to be cation (C12H8)n+ . Calculation shows that from n=0 to 6, molecule keeps its polycyclic hydrocarbon configuration. Whereas, at ionization step n=7, there occurs dehydrogenation of (C12H8) to pure carbon (C12). Such polycyclic pure carbon (PPC) would be attacked again by photons. At a stage of eighth ionization (C12)8+, there occur decomposition to aliphatic carbon chains, C9, C2, and mono carbon C1. Infrared spectra (IR) of those steps were calculated to identify observed spectra . Carrier molecules of Herbig Ae star WW Vul and HD145263 were identified by a combination of (C12H8)2+ and (C12H8)1+. Also, IR of HD37357 could be explained by (C12H8)2+, (C12H8)3+, and (C12H8)1+. Pure carbon molecules play an important role in many stars. IR of HD37258 was analyzed by a mixture of pure carbon (C12)2+, hydrocarbon (C12H8)2+ and neutral (C12H8)0+. Also, complex spectrum of HD38120 was analyzed by (C12)2+, (C12H8)2+ and (C12H8)3+. Acenaphthylene related molecules are just a typical example. We should apply various size molecules to understand total view around a new born star.
N. Ota
Wed, 28 Mar 18
61/148
Comments: 12pages, 10figures