Oxygen- and air-broadening coefficients for the CH3I ν6 fundamental at room temperature

Abstract CH 3 I-oxygen line-broadening coefficients at 296 K are calculated for the RR, PR, RP, PP, RQ and PQ sub-branches of the ν 6 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 CH 3 I-O 2 are further combined with the previously calculated room-temperature CH 3 I-N 2 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 CH 3 I-air measurements. As the vibrational dependence of CH 3 I oxygen-broadening coefficients is shown to be small, similarly to the nitrogen-broadening case, the CH 3 I-O 2 and CH 3 I-air line-broadening coefficients calculated for the ν 6 fundamental can be used for other perpendicular and parallel bands.