Line shape study of R-branch transitions in the ν[sub 1]+ν[sub 2]+ν[sub 4]+ν[sub 5] band of acetylene over a range of temperatures

Abstract

The temperature dependence of self‐broadened half width, pressure shift, and line asymmetry coefficients have been measured for twenty R‐branch transitions in the ν1+ν2+ν4+ν5 band of acetylene. All spectra were recorded using our 3 channel laser spectrometer, a temperature controlled cell of fixed length and a room temperature cell. The pressure shifts were obtained directly by comparing the line center positions of two simultaneous spectral profiles, one recorded at elevated pressure, and the other for the same line in pure acetylene at low pressure. The temperature was varied in steps of 20 K between 215 and 330 K. The pure acetylene profiles have been fitted by a Voigt profile. In addition, we have added a dispersion profile to account for weak line mixing. For each line the spectra recorded at the same temperature were analyzed using a multispectrum fitting program [3]. The experimental self broadening results were compared with similar measurements available in the literature. The self‐induced pressure shifts, line mixing coefficients and their temperature dependences were measured for the first time for transitions in this band.