Frequency shifts and lifetime changes of sodium atoms near rough metal surfaces

Two-photon laser-induced fluorescence measurements of transition frequencies and lifetimes of laser-excited Na atoms are presented as a function of distance (2-3 nm) to metal surfaces of different roughness. We characterized the surface roughness by fitting a Gaussian height-height correlation function to force microscopic data. An unusually small red shift of the Na transition frequency of a few hundred megahertz was observed. In the framework of a quantum-mechanical linear optical response formalism we fitted the lifetime and the frequency shift data simultaneously to obtain effective parameters of a selvedge dielectric function. In that way we are able to take into account both surface roughness and nonlocality, which in turn result in the observed small frequency shifts. (C) 1997 Optical Society of America.