Nitrogen Broadening of Acetylene Lines in the nu5 Band at Low Temperature.

N2-broadening coefficients have been measured for 22 lines of C2H2 at 173.4 K in the P and R branches of the nu5 band, using a tunable diode-laser spectrometer. The lines with J values ranging from 1 to 29 are located in the spectral range of 661-762 cm-1. The collisional widths obtained by Rautian profiles fitting closely the measured spectral shape of the lines are slightly larger than those derived from Voigt profiles. Semiclassical calculations of these broadenings have been performed by considering, in addition to electrostatic interactions, successively the atom-atom model and the Tipping-Herman intermolecular potential. The results obtained, which for some of them are in good agreement with the experimental data, depend significantly on the isotropic potential used to describe the trajectory model. By comparing broadening coefficients at room and low temperature, their temperature dependencies have been determined both experimentally and theoretically Copyright 1998 Academic Press.