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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
Subject(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.
Issue Date:6/21/2017
Publisher:International Symposium on Molecular Spectroscopy
Citation Info:APS
Genre:CONFERENCE PAPER/PRESENTATION
Type:Text
Language:English
URI:http://hdl.handle.net/2142/96807
DOI:10.15278/isms.2017.WJ02
Date Available in IDEALS:2017-07-27


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