Nonlinear evanescent wave spectroscopies: A close look at the gas-solid interface

The dynamics of atom/molecule scattering at surfaces plays a crucial role in such diverse applications as heterogeneous catalysis, chemical vapor deposition and aerodynamics. This process traditionally has been investigated with the use of atomic/molecular beams under ultra-high-vacuum conditions, i.e. far from the regime required in applications that has been formulated as a 'pressure gap' problem. The advantages of laser spectroscopy, however, suggest a principally new approach to this dilemma. In this paper we present recent results, both experimentally and theoretically, illustrating the potential of evanescent wave spectroscopy for surface science. We demonstrate how such fundamental features of gas-surface scattering as the scattering kernel, sticking probability and velocity distribution functions can be extracted from a careful analysis of nonlinear fluorescence spectra excited by both evanescent and non-evanescent waves. We also review the prospective developments of this technique which are based on a four-wave mixing process and Raman scattering in atoms/molecules near surfaces