Hydrogen-broadening coefficients in the ν5 band of acetylene at low temperature

H-2-broadening coefficients have been measured for 29 lines of C2H2 at 173.2 K in the P and R branches of the nu(5) fundamental band near 13.7 mum, using a tunable diode-laser spectrometer. These lines were individually fitted with a Voigt and a Rautian profile in order to determine the collisional widths. The resulting broadening coefficients are compared with values calculated from a semiclassical theory performed by considering, in addition to electrostatic interactions, the atom-atom Lennard-Jones model. A satisfactory agreement is obtained but only for low and medium J values. 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. (C) 2002 Elsevier Science (USA).