State resolved rotational relaxation of CS2 in argon free jet

Rotational relaxation of CS2 in argon free jet was studied using laser-induced fluorescence ~LIF!. The rotational populations were obtained from LIF detection at 19 different points along the jet axis from 3 to 15 nozzle diameters. On the basis of the energy gap power law, the master equation was solved to fit the experiment results, and the two temperature-independent parameters in the law were determined. The results show that the state-to-state relaxation cross sections vary as the inverse 1.7 power of the energy gap between the initial and the final states. The expressions for the state-to-state relaxation cross sections and the rate constants were written. The relaxation cross sections decrease with increasing temperature over the range of 2–60 K for the CS21Ar collision. © 1995 American Institute of Physics.