ANOMALOUS DRIFT OF RESONANT PARTICLES IN A BUFFER MEDIUM UNDER PRESSURE OF LIGHT

We study theoretically the drift of resonant particles in a buffer med ium when a traveling light wave impinges on the medium, with allowance for the velocity dependence of the transport collision rate. When the pressure of light dominates over the light-induced drift (low pressur e of the buffer gas or the drift of conduction electrons in semiconduc tors), we discover a new sudden transformation of the spectral depende nce of the drift velocity of the resonant particles: Instead of the or dinary bell-shaped function representing the velocity spectrum we have a double-humped curve with deep dip at the center of the absorption l ine. We show that the largest transformation of the drift velocity spe ctrum occurs in the atmosphere of a heavy buffer gas in the case of Co ulomb interaction between the resonant and buffer particles. The trans formation effect is caused by the variation of the transport rate of t he collisions of the resonant and buffer particles due to the recoil e ffect in the absorption of radiation. (C) 1997 American Institute of P hysics. [S1063-7761(97)00709-9].