Temperature dependence of N2- and O2-broadening coefficients in the ν4 band of 13CH4

Using a tunable diode laser spectrometer and an home made cooling cell, the N2- and O2-broadening coefficients of 13CH4 were measured at room and low temperatures in the ν4 band near 1300 cm-1. Fifteen transitions were studied for the 13CH4 diluted in the nitrogen at room temperature and 11 of them were also studied at 273.0 K, 248.0 K, 223.0 K, 198.0 K and 173.0 K. Twenty-four lines were considered at room temperature for the gas-mixture 13CH4+O2 and 10 of them were analyzed at low temperatures (273.0 K, 223.0 K and 173.0 K). The measurements at low temperatures allowed the determination of the temperature dependence parameter of the collisional broadening coefficients. The line parameters were obtained by fitting, to the experimental profile, the Voigt lineshape and the Rautian and Sobel'man model taking into account the collisional narrowing. In addition, air-broadening coefficients were calculated in the ν4 band of 13CH4 for 10 transitions studied jointly for the mixtures 13CH4+N2 and 13CH4+O2. We compare, in this paper, the collisional broadening coefficients determined at room temperature with previous studies on the ν3 and ν4 bands of 13CH4. The results are also confronted with N2- and O2-broadening coefficients determined in the ν4 band of 12CH4. The air-broadening coefficients, based on a simple atmospheric composition, are compared with HITRAN values.