Oxygen Broadening of Acetylene Lines in the ν₅ Band at Low Temperature

O-broadening coefficients have been measured for 29 lines of CHat 173.2 K in thePandRbranches of the νband near 14 μm, using a tunable diode-laser spectrometer. The collisional widths obtained by Rautian profiles closely fitting the measured spectral shape of the lines are slightly larger than those derived from Voigt profiles. The broadening coefficients are compared with results calculated from a semiclassical theory, performed by considering, in addition to electrostatic interactions involving the hexadecapole moments of CHand O, the atom-atom Lennard-Jones model. By comparing broadening coefficients at 297 and 173.2 K from a simple power law, the temperature dependence of these broadenings has been determined both experimentally and theoretically.