Diode Laser Measurements of Self-Broadening Coefficients in the v₅ Band of C₂H₂ at Low Temperature

Collisional self-broadening coefficients for 21 lines in the P and R branches of the v band of CH at low temperature (173 K) have been measured using a tunable diode laser spectrometer and a low-temperature variable path length absorption cell. These lines, with J values ranging from 1 to 25, are located in the spectral range 670-790 cm. A semiclassical line-broadening calculation provides satisfactory results when the electrostatic interactions arising from the hexadecapole moment of CH are taken into account. We have also examined the validity of a simple power law governing the temperature dependence of the broadening coefficients.