Collisional Relaxation in Low-Pressure Photolytic Iodine Lasers

Abstract

When the molecules in a gas are photolyzed by a short exitation pulse, the resulting initial velocity distribution can be broader and have a different mean velocity than the velocity distribution the gas has in thermal equilibrium. The velocity distribution then relaxes into thermal equilibrium, the mechanism for this relaxation being collisional. Using time-resolved Doppler spectroscopy, the corresponding relaxation time for C3F7I at 0.1 Torr has been measured to be approximately 5 μs [1], for example.