Two-photon laser spectroscopy of the gas boundary layer in crossed evanescent and volume waves - art. no. 012903

A spectroscopic approach to the scattering dynamics in the gas-surface boun dary layer is presented. The technique utilizes excitation of the vapor ato ms in two crossed laser fields, one of which is directed normally to the su rface while the other one excites an evanescent wave propagating along the surface. We provide a rigorous and quantitative theoretical description of these two-photon evanescent-volume wave spectra and apply it to the model s ystem of sodium atoms colliding with a dielectric prism surface. A comparis on with experimental results reveals quantitative agreement between theory and experiment. We demonstrate that one can distinguish by pure optical mea ns between different groups of atoms, namely atoms moving to the surface an d apart from it after being specularly or diffusively scattered. We also ex tract the two-dimensional velocity distributions of both the arriving and d eparting groups of atoms.