Shock-Tube Measurements of Vibrational Relaxation

Vibrational relaxation times at temperatures between 400°K and 1500°K have been measured in chlorine and carbon dioxide with a shock tube. The approach toward equilibrium vibrational excitation behind the shock wave is obtained from the density profile of the transition region using an optical interferometer. The measurements were made with a relatively narrow shock tube in order to avoid errors caused by optical distortions. The accuracies of the measured relaxation times are estimated to be from 20 percent to 50 percent.