LASER SPATIAL SATURATION SPECTROSCOPY: A NEW TOOL FOR STUDYING DIFFUSION PROCESSES

Abstract

A new technique for measuring diffusion coefficients and dynamic friction coefficients in the gas sample at low pressure is described. By varying the distance between two spatially separate antiparallel laser beams in a saturable absorber, we are able to follow the dynamics of the Bennett hole and the resonant spike, caused by the nonlinear absorption, in the molecular velocity distribution. Systems studied are pure $I_{2}, I_{2}$ in the presence of argon buffer gas, and $BO_{2}$ radicals. The present technique is also capable of measuring the diffusion coefficient of an excited state species. Table I summarizes the results.[FIGURE] Present address of Chung-Yung Robert Wu: Department of Chemistry, University of Iowa, Iowa City, Iowa, 52242.