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 CS2+Ar collision.