The Bending of C${}_3$: Experimentally Probing the $l$-type Doubling and Resonance

Abstract

C${}_3$, a pure carbon chain molecule that has been identified in different astronomical environments, is considered a good probe of kinetic temperatures through observation of transitions involving its low-lying bending mode (${\nu }_2$) in its ground electronic state. The present laboratory work aims to investigate this bending mode with multiple quanta of excitation by combining recordings of high resolution optical and infrared spectra of C${}_3$ produced in discharge experiments. The optical spectra of rovibronic (A ${}^1{\Pi }_u-$ X ${}^1{\Sigma }_g^{+}$) transitions have been recorded by laser induced fluorescence spectroscopy using a single longitude mode optical parametric oscillator as narrow bandwidth laser source at the University of Science and Technology of China. 36 bands originating from X(0$v_2$0), $v_2=0-5$, are assigned. The mid-infrared spectrum of the rovibrational ${\nu }_3$ band has been recorded by Fourier-transform infrared spectroscopy using a globar source on the AILES beamline of the SOLEIL synchrotron facility. The spectrum reveals hot bands involving up to 5 quanta of excitation in ${\nu }_2$. From combining analyses of all the presently recorded spectra and literature data, accurate rotational parameters and absolute energy levels of C${}_3$, in particular for states involving the bending mode, are determined. A single PGOPHER file containing all available data involving the X and A states (literature and present study) is used to fit all the data. The spectroscopic information derived from this work enables new interstellar searches for C${}_3$, not only in the infrared and optical regions investigated here but also notably in the ${\nu }_2$ band region (around 63 cm${}^{-1}$) where vibrational satellites can now be accurately predicted. This makes C${}_3$ a universal diagnostic tool to study very different astronomical environments, from dark and dense to translucent clouds.

arXiv comment15 pages, 9 figures, 4 tables

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Cited by in corpus (2)

• Data availability and requirements relevant for the Ariel space mission and other exoplanet atmosphere applications
• The EDIBLES Survey. VII. A survey of C2 and C3 in interstellar clouds