Determination of foreign broadening coefficients for Methane Lines Targeted by the Tunable Laser Spectrometer (TLS) on the Mars Curiosity Rover

Molecular line parameters of foreign- broadening by air, carbon dioxide, and helium gas have been experimentally determined for infrared ro-vibrational spectral lines of methane isotopologues (^(12)CH_4 and ^(13)CH_4) at 3057 cm^(−1) targeted by the Tunable Laser Spectrometer (TLS) in the Sample Analysis at Mars (SAM) instrument suite on the Mars Science Laboratory (MSL) Curiosity rover. From multi-spectrum analyses with the speed-dependent Voigt line profile with Rosenkrantz line-mixing, speed-dependence and line-mixing effects were quantified for methane spectra at total pressures up to 200 mbar. The fitted air-broadening coefficients deviated from 8–25% to those reported in the HITRAN-2012 database.