Reconnaissance of the uncharted low energy vibrational motions of acenaphthene

https://doi.org/10.1016/j.jms.2020.111296Get rights and content
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Highlights

  • Room temperature, millimeter-wave, rotationally resolved acenaphthene measurements.

  • Identification of six vibrational satellites of acenaphthene.

  • Line lists of all species from 75 to 110 GHz to facilitate astronomical searches.

Abstract

The room-temperature, millimeter-wave rotational spectrum of the small polycyclic aromatic hydrocarbon acenaphthene has been measured between 75 and 110 GHz. Accurate rotational and distortion parameters are presented due to the over 1400 transitions that have been included into a global fit. Besides observing transitions of the ground vibrational state, six vibrationally excited states have been identified: four fundamental modes (ν30,ν41,ν40,ν29), one overtone (2ν30), and one combination band (ν41+ν30). This is the first report of four of these excited states observed in the gas phase as two of the fundamental modes are IR inactive and the intensities of the overtone and combination bands are often too weak to be observed. These excited states reside less than 300 cm−1 above the ground state, and an experimental approximation of their band centers is presented. The rotational constants and line lists can be used to facilitate the search for this polycyclic aromatic hydrocarbon in the interstellar medium.

Keywords

Astrochemistry
Polycylic aromatic hydrocarbons
Vibrationally excited states
Millimeter-wave spectroscopy
Chirped-pulse Fourier transform rotational spectroscopy

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