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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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