Temperature dependence of near-infrared CO2 line shapes measured by cavity ring-down spectroscopy

Hodges, Joseph T.

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https://hdl.handle.net/2142/96807 Copy

Description

Title

Temperature dependence of near-infrared CO2 line shapes measured by cavity ring-down spectroscopy

Author(s)

Hodges, Joseph T.

Contributor(s)

• Liu, Qingnan
• Fleisher, Adam J.
• Ghysels, Mélanie

Issue Date

2017-06-21

Keyword(s)

• Lineshapes
• Collisional effects

Abstract

We present high signal-to-noise ratio, mode-by-mode cavity ring-down spectroscopy (CRDS) line shape measurements of air-broadened transitions in the 30013 $rightarrow$ 0001 band of $^{12}$C$^{16}$O$_2$ located near $lambda$ = 1.6 $mu$m. Absorption spectra were acquired from (230-290) K with a variable-temperature spectrometer developed in the framework of the NASA Orbiting Carbon Observatory-2 Mission to improve our understanding of carbon dioxide and oxygen line shape parameters. This system comprises a monolithic, thermally stabilized two-mirror, optical resonator exhibiting a mode stability of 200 kHz and a minimum detectable absorption coefficient of 10$^{-11}$ cm$^{-1}$. Observed spectra were modeled the using the recently recommended Hartmann-Tran line profile (HTP) footnote{Tennyson, et al., $textit{Pure Appl. Chem.}$ $textbf{86}$, (2014) 1931} (and several of its limiting cases) which includes the effects of Dicke narrowing, speed dependent broadening, correlation between velocity- and phase-changing collisions and first-order line mixing effects. At fixed temperature, line shape parameters were determined by constrained multispectrum fitting of spectra acquired over the pressure range (30 - 300) Torr. For each transition considered, analysis of the temperature dependence of the fitted line shape parameters yielded the pressure-broadening temperature exponent and speed dependence parameter, where the latter quantity was found to be in good agreement with theoretical values consistent with the HTP model.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/96807

DOI

https://doi.org/10.15278/isms.2017.WJ02

Copyright and License Information

Copyright 2017 Joseph T. Hodges

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