Measurement and prediction of Raman Q-branch line self-broadening coefficients for CO from 400 to 1500 K

The J and temperature dependence of the self-broadening coefficients for the Raman Q-branch lines of pure CO have been experimentally determined for Q(J) transitions with J=0–38 and for temperatures in the range 400–1500 K. It is shown that a fitting law, based on a modified exponential energy-gap model for the rates of state-to-state rotationally inelastic collisions, can account for the observed J dependence. The two parameters that determine the J dependence are found to be essentially independent of temperature. A temperature scaling function, recently proposed for N2, is added to the basic rate law, and accurate predictions of both the J and the T dependence of these coefficients and those previously reported at 298 K are obtained. This rate law model, used in conjunction with a relaxation matrix description of the Q-branch spectrum, is shown to give good agreement with the observed, partially collapsed spectrum at 2.8 atm and 295 K.