AN EQUATION FOR RESONANCE-RADIATION TRANSFER IN A HEAVY-ATOM GAS INJECTED INTO A RAREFIED ATMOSPHERE

An analytic description is given for the collision-perturbed expansion (CPE) of the neutral component of a heavy-atom gas injected into a ra refied atmosphere, and for the velocity-dependent transport cross-sect ion for barium-oxygen collisions. A closed equation is formulated for the transport of linearly-polarized resonance radiation in a non-Maxwe llian gas composed of two-level, zero-spin atoms. Analytic results are obtained for the local values of the absorption coefficient and photo n redistribution function, which extend the respective quantities for Doppler broadening of the spectral lines in a Maxwellian gas to the ca se of the CPE gas. It is shown that even for almost free expansion of the artificial cloud, the spectral line width of injected heavy atoms may be determined by non-equilibrium Doppler-type broadening, caused b y their collisions with atmospheric atoms. The results may be generali zed to the case of multilevel kinetics, arbitrary photon polarization and atomic spin.