Probing the spatial dispersion in a dense atomic vapor near a dielectric interface

We have experimentally investigated the selective reflection of the P-D tra nsition in a high-density rubidium vapor and shown it to be sensitive to th e exact spatial distribution of P-state atoms near the dielectric-vapor int erface. This distribution results from the radiative and nonradiative trans port of excitation and from wall-quenching collisions of excited-state atom s and is highly inhomogeneous. Selective reflection thus acts as a probe of the spatial dispersion in the vapor. The resulting spectra have been analy zed to show that the broadening due to S-D collisions contributes considera bly to the self-broadened linewidth of the P-D transition. [S1050-2947(98)0 7712-9].