On the nature and decay of electronically excited states at metal surfaces

We present a qualitative discussion of the nature and nonradiative decay of electronically excited states at metal surfaces. Within an Anderson–Newns type of Hamiltonian, we calculate, using the memory function formalism, the effect of the substrate on the energy and shape of the optical absorption or electron energy loss spectra and present illustrative numerical results. The theory is compared with experimental data for excited noble gas atoms on noble metal surfaces.