Temperature-dependence exponents for CH3I-N2 line-broadening coefficients

International audienceTemperature-dependence exponents of the traditional power law relating line-broadening coefficients at experimental and reference temperatures are deduced for CH3I-N2 lines in the ν6 band from theoretical estimates in the temperature interval 200–400 K recommended for HITRAN. Perfectly linear fits in log-log coordinates indicate that this simple law is sufficient and more advanced models such as the double-power law are not applicable. Calculations are performed by a semi-empirical method employing room-temperature-adjusted model parameters which remain valid for other temperatures. Results are provided for all six sub-branches of the considered band and cover a large range of quantum numbers (0 ≤ J ≤ 70, K ≤ 20) requested typically by spectroscopic databases. In the absence of measurements at not-room temperatures, these data can be extremely useful for atmospheric applications involving methyl iodide, in particular for the terrestrial atmosphere. Given the negligible vibrational dependence of nitrogen-broadened CH3I line widths, the values computed for the ν6 fundamental can be safely used for other parallel and perpendicular bands

Vibrational shifts of absorption bands of linear molecules diluted in high-density rare gases: Measurements and modeling for CO2-Rg and OCS-Rg

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Temperature dependence of CH3I self-broadening coefficients in the ν6 fundamental

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Oxygen- and air-broadening coefficients for the CH 3 I ν 6 fundamental at room temperature

International audienceCHI-oxygen line-broadening coefficients at 296 K are calculated for the RR, PR, RP, PP, RQ and PQ sub-branches of the band in a wide range of rotational quantum numbers (, 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 and . The theoretical data for CHI-O are further combined with the previously calculated room-temperature CHI-N 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 CHI-air measurements. As the vibrational dependence of CHI oxygen-broadening coefficients is shown to be small, similarly to the nitrogen-broadening case, the CHI-O and CHI-air line-broadening coefficients calculated for the fundamental can be used for other perpendicular and parallel bands

Room-temperature CH 3 I-N 2 broadening coefficients for the ν 6 fundamental

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Line parameters measurements and modeling for the ν6 band of CH3I: A complete line list for atmospheric databases

International audienceThe present work is dedicated to the ν6 band of 12CH3I with the aim of generating a complete line list for databases. High resolution Fourier transform spectra have been recorded in MONARIS and a multispectrum fitting procedure using Voigt profile has been applied to retrieve line positions, intensities, and self-broadening coefficients for around 1200 transitions of the ν6 band between 854 and 963 cm−1. Rotational dependences of transition dipole moment squared and self-widths have been studied and empirically modeled. Line positions are retrieved with accuracy equal to 4.10−4 cm−1. The accuracy of line intensities and self-widths measurements is estimated between 5 and 10 %. Theoretical estimates of CH3I self-broadening coefficients for large ranges of rotational quantum numbers (0 ≤ J ≤ 70, 0 ≤ K ≤ 20) are also provided in the frame of a semi-classical approach with exact trajectories and of a semi-empirical method including a correction factor to the Anderson-type line-width expression. Comparisons of our results with the data previously published in the literature are presented and discussed. A complete line list of 5787 transitions is generated. Available as supplementary material, this line list can be used for spectroscopic databases and atmospheric or industrial detection of CH3I