THE FAR-INFRARED EMISSION FROM THE Mg+-PAH SPECIES

The far-infrared (FIR) spectra of several Mg+-PAH species are studied using density functional theory. The Mg+-PAH stretching mode, regardless of the polycyclic aromatic hydrocarbon (PAH) species, carries a reasonable intensity and tends to fall in a narrow range near 40 mu m. Because the bands tend to fall at very similar frequencies, the average spectra of several Mg+-PAH species produce a broadband with an intensity that is about 20% of the well known C-H out-of-plane bending mode. In contrast, an average of seven large compact pure PAHs has no FIR bands that carry any significant intensity.