Narrow band emission from Au-film on Cu- substrate

The experiments reveal the strong narrow band in the spectra of the emission from Au-film on the Cu substrate. The emission was excited by red He-Ne laser in standard geometry for Raman back-scattering experiments. Some additional experiments were made. The set of obtained data did not give enough arguments to make the final conclusion about the nature of this emission. The details of experiments, results, and possible explanations are discussed.