LIFETIME OF SURFACE-PLASMONS OF SIMPLE METALS - VOLUME VERSUS SURFACECONTRIBUTIONS

The influence of the bulk lattice potential on the surface plasmons of simple metals is studied using a one-dimensional crystalline model. T he model potential consists of a smooth Lang-Kohn surface barrier and a sinusoidal bulk potential in the direction normal to the surface. Th e surface excitation spectra that can be compared to electron-energy-l oss measurements are calculated within the random-phase approximation. At small parallel wave vectors, the plasmon field decays slowly, and the width of the surface-plasmon peak is a sensitive function of the b ulk lattice potential. At larger wave vectors, the plasmon field is mo re localized near the surface. The coupling to bulk interband transiti ons is then reduced, and the lifetime is dominated by loss processes i nduced by the surface barrier.