Experimental investigation of the nonequilibrium velocity distribution function in a heat conducting gas

Preliminary measurements of the nonequilibrium velocity distribution function in a heat conducting gas have been carried out using a Doppler broadened absorption line. The experimental technique, which uses the coincidence of a Stark tunable line of NH2D and the CO2 P(20) laser frequency, is described. For molecular velocities that are not too high, the results are in good agreement with the Chapman-Enskog solution of the Boltzmann equation.