Self-collisional broadening and shift coefficients of lines in the v₄+v₅ band of C₂¹²H₂ from 173.2 to 298.2K by diode-laser spectroscopy

The pressure-induced self-shift and broadening coefficients for seven lines of C212H2 in the v4+v5 band located around 1330cm have been measured using a tunable diode-laser spectrometer coupled with a low temperature absorption cell. The measurement of these coefficients was realized at five temperatures ranging from 173.2 to 273.2K (and also 298.2K for shift) in order to determine their temperature dependence. The broadening coefficients were obtained by fitting to the experimental profile the Voigt lineshape and the Rautian and the Galatry models which take into account the collisional narrowing due to molecular confinement (Dicke effect). The shift coefficients were determined using a procedure, where calibration lines were simultaneously recorded with transitions from the gas sample under study. The results have been compared with previous experimental data. Our coefficients of collisional broadening, γ0, as well as the temperature dependence parameters, n, are in satisfactory agreement with previous studies. The pressure broadening coefficients, γ0, are in good agreement with those reported for various vibrational bands, indicating that they are insensitive to vibrational excitation. The pressure shift coefficients, δ0, by contrast, are found to differ substantially among vibrational bands.