Line-mixing effects in He- and N2-broadened Q branches of C2H2 at low temperatures

Two Q branches Of C2H2 near 716.3 and 719.9 cm(-1) of Sigma <-- Pi symmetry have been studied for He and N-2 perturbers at pressures ranging from 0.05 to 0.8 atm and low temperatures (-75 and -90 degreesC) using a tunable diode-laser spectrometer. To interpret the strong line-mixing effects observed in these spectra, we have applied a model based on the energy corrected sudden approximation (ECS) whose parameters are derived from those previously determined at room temperature through a fitting procedure of line-broadening coefficients. These coefficients have been measured for a few lines of C2H2 perturbed by He at -100 degreesC. The ECS model provides satisfactory agreement with experimental bandshapes for both bands, temperatures and perturbers at pressures generally higher than 0.1 atm. (C) 2001 Elsevier Science.