Oxygen- and air-broadening coefficients for the CH[formula omitted]I [formula omitted] fundamental at room temperature

Abstract

CH3I-oxygen line-broadening coefficients at 296 K are calculated for the RR, PR, RP, PP, RQ and PQ sub-branches of the ν6 band in a wide range of rotational quantum numbers (0≤J≤70, K≤20 by a semi-classical and a semi-empirical methods. The computed values compare very favourably with the available experimental data and therefore can be safely employed as estimates of broadening coefficients missing in databases for high J and K. The theoretical data for CH3I-O2 are further combined with the previously calculated room-temperature CH3I-N2 line-broadening coefficients to obtain the air-broadening values required for atmospheric applications. The calculated results demonstrate an excellent consistency with both existing sets of CH3I-air measurements. As the vibrational dependence of CH3I oxygen-broadening coefficients is shown to be small, similarly to the nitrogen-broadening case, the CH3I-O2 and CH3I-air line-broadening coefficients calculated for the ν6 fundamental can be used for other perpendicular and parallel bands.