| Name: | VISHNU PATEL |
| Affiliation: | Deen Dayal Upadhyaya Gorakhpur University Gorakhpur |
| Conference ID : | ASI2024_785 |
| Title : | Vibrational Spectroscopy of Super-Ring Molecule |
| Authors : | Vishnu Patel*, Anju Maurya, Shantanu Rastogi
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| Authors Affiliation: | Department of Physics, Deen Dayal Upadhyaya Gorakhpur University Gorakhpur, Civil lines, Gorakhpur -273009
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| Mode of Presentation: | Poster |
| Abstract Category : | Stars, Interstellar Medium, and Astrochemistry in Milky Way |
| Abstract : | Polycyclic aromatic hydrocarbons (PAHs) are commonly believed to be the carriers of the aromatic infrared bonds (AIBs) that dominate the mid-IR emission at 3.3, 6.2, 7.7, 8.6, 11.2, and 12.7 micron in most galactic and extra galactic objects. It is considered that PAHs form in carbon rich circumstellar envelopes. Large PAHs appear to show spectral corelation with AIBs in late type stars. The super ring molecule [Kekulene; C48H24] is a possible aromatic molecule in such regions. It is essentially a large, planar, and fully conjugated cyclic carbonaceous molecule, with a coronene type structure missing in the centre. The molecule consists of 12 benzene rings interconnected in a circle. Each benzene ring shares alternating carbon atoms with neighbouring rings, resulting in a highly conjugated system. Quantum chemical DFT computations are performed using B3LYP functionals in conjugation with 6-31Gd basis set through the GAMESS suit of programs. The computed IR spectra of the super ring Kekulene is studied in both neutral and cation state. The variation in bond lengths, charge distribution and vibrational frequencies are studied. The molecule has unique vibrational signatures. In neutral: there is strong feature of C-H stretch modes (3038 cm-1) and dominant features of C-H out of plane vibrations (885 cm-1) and C-C stretch and C-H in-plane vibrations (1233 cm-1). In cation: C-H stretch mode intensity vanishes, just as in plain PAH molecules, and the C-C stretch and C-H in plane modes gain intensity. In both neutral and cation, the is C-H out of the plane vibration modes remain significant. The prospect of Kekulene and similar carbonaceous structures is discussed in context of astrophysical AIBs. The mechanism of formation of such PAHs and their contribution to the observed infrared bands and their sub features may pave the way to a better understanding of the evolution of the late type stars. |
