Line mixing effect in the ν2 band of CH3Br

Abstract Line intensities, self broadening coefficients, as well as line mixing parameters and self-shift coefficients have been measured in the ν 2 parallel band of CH 3 Br at room temperature for 38 rovibrational doublets with rotational quantum numbers 4≤ J ≤47 and K =0, 1. Measurements were made in the P and R branches located in the spectral range from 1260 to 1332 cm −1 using high-resolution Fourier transform spectra. These spectroscopic parameters have been retrieved from twelve spectra recorded at different pressures of pure CH 3 Br from 0.2 to 6.8 Torr. The spectra have been analyzed using a multi-pressure non-linear least squares fitting of Rosenkranz profile taking into account line mixing effect. These spectra and results of pressure broadening coefficients and line intensities obtained with and without taking into account line mixing effect are compared, analyzed and discussed as function of the rotational quantum numbers and the branch. Analyzing of overlapped lines demonstrates an important mixing effect between the doublets components. On average the values of these spectroscopic parameters obtained when taking into account line mixing were found to be about 5% smaller than those obtained without taking into account this effect. On average, the accuracies of self-broadening coefficients and line intensities are estimated to be better than 3.8%. The mean accuracies of line-mixing and line-shift data are estimated to be about 20% and 17% respectively. The measured line mixing parameters are both positive and negative, while most of the lines have a negative shift coefficient.