Infrared spectra of methyl-, and nitrogen-modified void coronene;
  modeling a carrier of interstellar polycyclic aromatic hydrocarbon
  Void induced coronene C23H12++ was suggested to be a possible carrier of the
astronomically observed polycyclic aromatic hydrocarbon (PAH), which shows
unique molecular structure with carbon two pentagons connected with five
hexagons. Well observed astronomical infrared spectrum from 3-15 micron could
be almost reproduced based on density functional theory. However, there remain
several discrepancies with observed spectra, especially on 11-15 micron band
weaker intensity. Observed 11.2 micron intensity is comparable to 7.6-7.8
micron one. Methyl-modified molecule C24H14++ revealed that calculated peak
height of 11.4 micron show fairly large intensity up to 70-90% compared with
that of 7.6-7.8 micron band. Also, nitrogen atom was substituted to peripheral
C-H site of void coronene to be C22H11N1++. Pentagon site substituted case show
60% peak height. This molecule also reproduced well 12-15 micron peak position
and relative intensity. Vibration mode analysis demonstrated that 11.3 micron
mode comes from C-H out of plane bending. Heavy nitrogen plays as like an
anchor role for molecule vibration.
