Investigating C-D out-of-plane vibrational modes in PAHs as a tool to study interstellar deuterium-containing PAHs
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| Format: | Preprint |
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2024
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| _version_ | 1866912268975865856 |
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| author | Buragohain, Mridusmita Onaka, Takashi Pathak, Amit Vats, Akant Sakon, Itsuki |
| author_facet | Buragohain, Mridusmita Onaka, Takashi Pathak, Amit Vats, Akant Sakon, Itsuki |
| contents | Previous as well as recent observations by ISO, Spitzer, AKARI, SOFIA, JWST etc. have revealed various characteristics of mid-infrared emission bands between 3-20 micron. Subsequently, several forms of organics including Polycylic Aromatic Hydrocarbons (PAHs)/PAH-like molecules are proposed as carriers for these bands. Deuterated PAH (PAD) is one such substituted PAH, which is proposed as a potential candidate carrier for weak emission bands at 4.4 and 4.65 micron, detected towards few astronomical targets and are characteristics of aromatic and aliphatic C-D stretching modes in a PAD molecule, respectively. However, the 4.4 micron band is not widely detected. In order to validate PADs as carriers for mid-infrared emission bands, an additional alternative tool is crucial. If PAHs are deuterated, they should also possess an inherent signature from the C-D out-of-plane (C-Doop) vibrations, which are at the longer wavelength side. In this report, features due to C-Doop modes in PAHs bearing a single to multiple deuterium atoms are reported by performing quantum-chemical calculations. This paper reports that some of the C-Doop vibrations appear at the 14-19 micron range. Also, the strength of C-Doop modes is not proportional to the D/H ratio in PAHs. In addition, a moderate change in the spectra of deuterated PAHs is observed from that of the undeuterated counterparts, as deuteration would alternate the adjacency class of the C-H bonds and the symmetry of the molecule. We discuss the efficiency and usefulness of these bands to constrain the form of PAHs emitting mid-infrared emission bands. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2409_13444 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Investigating C-D out-of-plane vibrational modes in PAHs as a tool to study interstellar deuterium-containing PAHs Buragohain, Mridusmita Onaka, Takashi Pathak, Amit Vats, Akant Sakon, Itsuki Astrophysics of Galaxies Solar and Stellar Astrophysics Previous as well as recent observations by ISO, Spitzer, AKARI, SOFIA, JWST etc. have revealed various characteristics of mid-infrared emission bands between 3-20 micron. Subsequently, several forms of organics including Polycylic Aromatic Hydrocarbons (PAHs)/PAH-like molecules are proposed as carriers for these bands. Deuterated PAH (PAD) is one such substituted PAH, which is proposed as a potential candidate carrier for weak emission bands at 4.4 and 4.65 micron, detected towards few astronomical targets and are characteristics of aromatic and aliphatic C-D stretching modes in a PAD molecule, respectively. However, the 4.4 micron band is not widely detected. In order to validate PADs as carriers for mid-infrared emission bands, an additional alternative tool is crucial. If PAHs are deuterated, they should also possess an inherent signature from the C-D out-of-plane (C-Doop) vibrations, which are at the longer wavelength side. In this report, features due to C-Doop modes in PAHs bearing a single to multiple deuterium atoms are reported by performing quantum-chemical calculations. This paper reports that some of the C-Doop vibrations appear at the 14-19 micron range. Also, the strength of C-Doop modes is not proportional to the D/H ratio in PAHs. In addition, a moderate change in the spectra of deuterated PAHs is observed from that of the undeuterated counterparts, as deuteration would alternate the adjacency class of the C-H bonds and the symmetry of the molecule. We discuss the efficiency and usefulness of these bands to constrain the form of PAHs emitting mid-infrared emission bands. |
| title | Investigating C-D out-of-plane vibrational modes in PAHs as a tool to study interstellar deuterium-containing PAHs |
| topic | Astrophysics of Galaxies Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2409.13444 |