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

Abstract

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.

Surface enhanced fluorescence

“…Experimentally, the measured shifts are rather small. They increase with decreasing lifetime, from a few megahertz for Eu 3+ with τ ≈ 1 ms to a gigahertz for Na atoms with τ ≈ 1 ps [28].…”

Single-molecule spectroscopy near structured dielectrics

“…Several researchers have studied the emission properties of an ensemble of dye molecules on rough surfaces and gratings [10,11,12,13]. Very recently there have been also some efforts on the spectroscopy of atoms placed on a thin organic layer above a rough surface [14].…”

Electroluminescence properties of organic nanostructures studied by scanning tunnelling microscopy

“…A second possible lifetime reduction may be induced by non‐radiative quenching due to the proximity of metal substrate and STM tip. Time resolved experiments and theoretical results suggest that the life time of an emitting state may become shorter than 1 ns at distances from the metal below 3 nm 73–75. Without further investigations, we can thus not exclude that the presence of substrate and tip may prohibit the observation of the photon anti‐correlation.…”