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 Title: H2 BROADENING IN THE ν3 AND ν4 BANDS OF CH4 AT ROOM TEMPERATURE Author(s): Gharib-Nezhad, Ehsan Contributor(s): Bechtel, Hans A; Stark, Glenn; Line, Michael R.; Lyons, James R.; Heays, Alan Subject(s): Linelists, Lineshapes, Collisions Abstract: Methane (CH$_{4}$) is the dominant carbon-bearing molecule in terrestrial and exoplanetary atmospheres where the temperature is below 1000 K. Therefore, knowing its pressure-induced H$_{2}$-broadened absorption cross section is fundamental for exoplanetary atmospheric modeling. In this study, the pressure-induced H$_{2}$-broadening coefficients of CH$_{4}$ are determined in the spectral regions ~2800-3200 ($\nu$$_3) and 1200-1400 cm^{-1} (\nu$$_4$). The laboratory transmission spectra in this study were recorded at high resolution (i.e., 0.005 and 0.01 cm$^{-1}$) at room temperature with an FTIR 125HR Bruker spectrometer at Lawrence Berkeley National Laboratory. The CH$_{4}$ pressure was constant during the entire experiment (29 mtorr), and elevated H$_2$ pressures were used in the range 100-700 torr. The Lorentzian coefficients are determined by a nonlinear regression approach in order to model the relationship between the linewidth and its corresponding pressure. Our preliminary results show that the Lorentzian coefficients of different lines in these two bands fall in the range 0.06-0.09 cm$^{-1}$/atm, consistent with the previous available measurements. Atmospheric modeling will be employed using exoplanet forward transmission modeling to highlight the importance of H$_{2}$-broadening of CH$_{4}$ to exoplanetary observations. Issue Date: 06/18/18 Publisher: International Symposium on Molecular Spectroscopy Citation Info: APS Genre: Conference Paper / Presentation Type: Text Language: English URI: http://hdl.handle.net/2142/100489 DOI: 10.15278/isms.2018.MI03 Other Identifier(s): MI03 Date Available in IDEALS: 2018-08-172018-12-12
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