Astronomical chemical evolution from graphene to polycyclic aromatic
  hydrocarbon reproducing observed infrared spectrum
  Interstellar ubiquitous infrared spectrum (IR) due to polycyclic aromatic
hydrocarbon (PAH) was observed in many astronomical dust clouds. A capable
astronomical chemical evolution path from graphene to PAH was studied based on
the first principles calculation. Step 1 is a nucleation of nano-carbon after
supernova by super-cooling at expanding helium sphere. As a typical model,
graphene molecule (C )24 having coronene skeleton with seven carbon hexagons
was tried.Step 2 is a proton sputtering and passivation on ejected graphene
molecule. Slow speed proton with energy less than 4.3eV makes hydrogenation,
Graphene molecule (C )24 was transformed to PAH (C24H12). Higher speed proton
having sufficient energy larger than 18.3 eV could make a void in a molecule as
like C23H12. Resulted structure was a combination of two carbon pentagons and
five hexagons. Step 3 is photo-ionization of those molecules by high energy
photon. Electrons are removed to make a molecule to cation. Model molecule
(C23H12) became mono-cation (C23H12)+, di-cation (C23H12)2+ and so on. Typical
energy difference between such cation was 6.5 and 10.8 eV. If the light source
has a nature of black-body radiation, effective temperature will be 18000K ~
24000K, which suggested that central light source star may have 4 to 7 times
heavier than our sun. Finally, theoretical IR spectrum was obtained. Especially
in case of (C23H12)2+, calculated emission spectrum revealed that among 13
major peaks, 11 peaks could correlate with ubiquitous observed IR one.
