Collisional broadening and shift coefficients of lines in the ν 4+ν 5 band of 12C 2H 2 diluted in N 2 from low to room temperatures

Abstract

The pressure-induced N 2 shift and broadening coefficients for nine lines of 12 C 2 H 2 in the ν 4 + ν 5 band located around 1330 cm − 1 were measured using a tunable diode-laser spectrometer coupled with a low temperature absorption cell. The measurement of these coefficients was realized at six temperatures (between 173.2 and 298.2 K) in order to determine their temperature dependence. The broadening coefficients were obtained by fitting the Voigt lineshape, and the Rautian and the Galatry models which take into account the collisional narrowing due to molecular confinement, to the experimental profile. The shift coefficients were determined using a procedure where calibration lines were simultaneously recorded with transitions from the gas sample under study. In order to detect a possible velocity effect of the C 2 H 2 − N 2 mixture, concentration and pressure dependences of the broadening coefficient were realized for five lines at room temperature. The results are compared with previous experimental data and also calculations. Our coefficients of collisional broadening, γ 0 , obtained at different temperatures as well as the temperature dependence parameter, n, are in satisfactory agreement with previous studies. The pressure broadening coefficients, γ 0 , are usually in good agreement with those reported for the same and other vibrational bands, indicating that they are insensitive to vibrational excitation. The pressure shift coefficients, δ 0 , by contrast, were found to differ substantially among vibrational bands.