Vibrational spectroscopy of interstellar PAHs: 1-cyanonaphthalene and 2-cyanonaphthalene
Vandana Rawat1, Aparna Shastri1, Asim K Das2
1Atomic & Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India; Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India.
Abstract:
In this work, we present a comprehensive experimental and theoretical study of the vibrational spectra of PAH molecules recently detected in the interstellar medium: 1-cyanonaphthalene and 2-cyanonaphthalene. The room temperature IR spectra of 1- and 2-cyanonaphthalene in the region 100-3100 cm-1 and their vibrational Raman spectra in the region 35-3100 cm-1 are reported here for the first time. A detailed spectral analysis is carried out using quantum chemical calculations employing the DFT methodology. Anharmonic corrections using the VPT2 method yield excellent agreement with the experimental spectra. A re-investigation of the vibrational spectrum of the parent molecule: naphthalene validates the experimental and theoretical methods used. A consistent set of assignments is reported for the fundamental bands of 1- and 2-cyanonapththalene. The experimental and theoretical data presented here would be useful inputs for modelling the role of cyanonaphthalene in astrophysical processes.
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