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 (2-3nm) 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.
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