Near-infrared spectroscopy of ethynyl radical, C2H

Le, Anh T.

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https://hdl.handle.net/2142/91216 Copy

Description

Title

Near-infrared spectroscopy of ethynyl radical, C2H

Author(s)

Le, Anh T.

Contributor(s)

• Sears, Trevor
• Hall, Gregory

Issue Date

2016-06-23

Keyword(s)

Radicals

Abstract

The ethynyl radical, \chem{C_2H}, is a reactive intermediate important in various combustion processes and also widely observed in the interstellar medium. In spite of extensive previous spectroscopic studies, the characterization of the near infrared transitions from the \textit{\~{X}}$^{2}$$\Sigma$$^{+}$ state to the mixed vibrational overtone and \textit{\~{A}}$^{2}$$\Pi$ states is incomplete. A strong band of \chem{C_2H} at 7064 cm$^{-1}$ was first observed in a neon matrix and assigned as the \textit{\~{A}}$^{2}$$\Pi$(002)$^{1}$ – \textit{\~{X}}$^{2}$$\Sigma$$^{+}$ transition by Forney et al.\footnote{D. Forney, M.E. Jacox, and W.E. Thompson, J. Mol. Spectrosc. 170, 178 (1995).} Subsequent theoretical work of Tarroni and Carter\footnote{R. Tarroni and S. Carter, Mol. Phys. 102, 2167 (2004).} attributed the strong absorptions in this region to transitions terminating in two upper states, each a mixture of vibrationally excited \textit{\~{X}} states and different zero-order \textit{\~{A}}-state bending levels: a $^{2}$$\Sigma$$^{+}$ symmetry combination of \textit{\~{X}}(0,2$^{0}$,3) and \textit{\~{A}}(0,3,0)$^{0}$$\kappa$ and a $^{2}$$\Pi$ symmetry combination of \textit{\~{X}}(0,3$^{1}$,3) and \textit{\~{A}}(0,0,2)$^{1}$. Transitions to them from the zero point level of the \textit{\~{X}} state are calculated to differ in energy by less than 10 cm$^{-1}$ and to be within a factor of two in intensity. Diode laser transient absorption was used to record Doppler-limited spectra between 7020 and 7130 cm$^{-1}$, using 193 nm photolysis of \chem{CF_3C_2H} as a source of \chem{C_2H}. Two interleaved, rotationally resolved bands were observed, consistent with a $^{2}$$\Sigma$ - $^{2}$$\Sigma$ transition at 7088 cm$^{-1}$ and a $^{2}$$\Pi$ - $^{2}$$\Sigma$ transition at 7108 cm$^{-1}$, in good accord with the Tarroni and Carter calculation. Progress on the assignment and fitting of the spectra will be reported. Acknowledgements: Work at Brookhaven National Laboratory was carried out under Contract No. DE-SC0012704 with the U.S. Department of Energy, Office of Science, and supported by its Division of Chemical Sciences, Geosciences, and Biosciences.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

En

Permalink

http://hdl.handle.net/2142/91216

Sponsor(s)/Grant Number(s)

Work at Brookhaven National Laboratory was carried out under Contract No. DE-SC0012704 with the U.S. Department of Energy, Office of Science, and supported by its Division of Chemical Sciences, Geosciences, and Biosciences.

Copyright and License Information

Copyright 2016 by the authors

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