Measurements of line intensities for some lines of methyl iodide in the ν5 and ν3 + ν6 bands
Abstract
The line intensities for RR- and PP- sub-branch transitions in the ν5 and ν3 + v6 bands of CH3I are measured for the first time for 270 lines with 5 ≤ J ≤ 40 and 4 ≤ K ≤ 11 using a multi-pressure fitting method with a Voigt profile. Seven spectra have been recorded using the Bruker IFS125HR Fourier Transform Spectrometer at the AILES beamline of SOLEIL Synchrotron with a resolution of 0.002 cm-1 for pressures between 0.270 and 2.433 mbar. Line intensities are analyzed and discussed as a function of the rotational quantum numbers. On average, the accuracy of the measured data is estimated to be about 4.5% for the two bands. The measured line intensities have been used to derive the vibrational transition moment, the Herman-Wallis parameters as well as the intensities of the two bands. The values for the band strengths of the ν5 and ν3 + v6are respectively 46.47 ± 2.63 cm-2 atm-1 and 14.79 ± 1.60 cm-2 atm-1. The measured line intensities were reproduced with mean values of difference of about 8.3% and 3.8% for the ν5 and ν3 + v6 bands respectively. At pressure used in this work, analysis of the overlapped line using the Rosenkranz profile demonstrates a negligible line-mixing effect on line intensities.