RECOIL AND MOMENTUM DIFFUSION OF AN ATOM CLOSE TO A VACUUM-DIELECTRICINTERFACE

We derive the quantum-mechanical master equation (generalized optical Bloch equation) for an atom in the vicinity of a flat dielectric surfa ce. This equation gives access to the semiclassical radiation pressure force and the atomic momentum diffusion tensor, that are expressed in terms of the vacuum field correlation function (electromagnetic field susceptibility). It is demonstrated that the atomic center-of-mass mo tion provides a nonlocal probe of the electromagnetic vacuum fluctuati ons. We show in particular that in a circularly polarized evanescent w ave: the radiation pressure force experienced by the atoms is not coli near with the evanescent wave's propagation vector. In a linearly pola rized evanescent wave: tie recoil per fluorescence cycle leads to a ne t magnetization for a J(g) = 1/2 ground state atom.