DFT Study On Interstellar PAH Molecules With Aliphatic Side Groups

Polycyclic Aromatic Hydrocarbon (PAH) molecules have been long adjudged to contribute to the frequently detected distinct emission features at 3.3, 6.2, 7.7, 8.6, 11.2 and 12.7 {\mu}m with weaker and blended features distributed in the 3-20 {\mu}m region.

The comparatively weaker 3.4 {\mu}m emission feature has been attributed to have an aliphatic origin as carrier. PAH with aliphatic functional group attached to it is one of the proposed potential candidate carriers for the 3.4 {\mu}m emission band, however, the assignment of carrier is still enigmatic. In this work, we employ Density Functional Theory (DFT) calculation on a symmetric and compact PAH molecule; coronene (C24H12) with aliphatic side group to investigate any spectral similarities with observed features at 3-4 {\mu}m. The side groups considered in this study are -H (hydrogenated), -CH3 (methyl), -CH2-CH3 (ethyl) and -CH=CH2 (vinyl) functional groups. Considering the possible presence of deuterium (D) in PAHs, we also include D in the aliphatic side group to study the spectral behavior. We present a detailed analysis of the IR spectra of these molecules and discuss possible astrophysical implications.

Mridusmita Buragohain, Amit Pathak, Itsuki Sakon, Takashi Onaka
(Submitted on 24 Mar 2020)

Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
Journal reference: The Astrophysical Journal, 892:11 (11pp), 2020 March 20
DOI: 10.3847/1538-4357/ab733a
Cite as: arXiv:2003.10691 [astro-ph.GA] (or arXiv:2003.10691v1 [astro-ph.GA] for this version)
Submission history
From: Mridusmita Buragohain
[v1] Tue, 24 Mar 2020 07:13:58 UTC (2,157 KB)
https://arxiv.org/abs/2003.10691
Astrobiology, Astrochemistry