Dynamical response and surface excitations in thin films

The non-local dynamically screened Coulomb interaction propagator W(Q, z, z ', omega) in the vicinity of thin metal film is calculated for points insi de and outside of the film, taking both collective modes and single-particl e excitations into account. This is achieved by calculating the non-local d ielectric function epsilon (p)(Q, z, z ', omega) of the thin jellium film w ithin the Random Phase Approximation (using Local Density Approximation wav e-functions), from which we then derive W(Q, z, z ', omega). The calculated dielectric function is also used to obtain excitation spectra, and specifi cally dispersion relations of the collective modes.