Line mixing in the QQ sub branches of the ν1 band of methyl chloride

Line-mixing effects have been studied in the ν1QQK (K from 0 to 10) sub branches of methyl chloride (CH3Cl) perturbed by nitrogen (N2). Laboratory Fourier transform spectra have been recorded at room temperature for various pressures of atmospheric interest. In order to accurately model these spectra, a theoretical approach accounting for line-mixing effects is necessary and proposed in this study. The common model used in this work is based on the state-to-state rotational cross-sections calculated by a statistical modified exponential-gap fitting law depending on few empirical parameters. These parameters have been deduced by least-squares fitting a sum rule to the N2-broadening coefficients modeled previously. Comparisons between experimental and calculated spectra for various QQ sub branches at various pressures of N2 demonstrate the adequacy of the model as compared to the use of the Voigt profile.

► FTS high-resolution study of methyl chloride at 3.4 μm. ► Line-mixing effects in the QQ sub branches of the ν1 band of CH3Cl. ► Direct calculation of the matrix operators.