Many-body effects in simple metal surfaces

equations are used to describe the electromagnetic field of the photon, wherein the electron system enters via the material equations. Using Green's functions, the Schroedinger equation with the perturbing Hamiltonian describing the photon field is solved for the scattering amplitude for various angles of photon penetration and electron emission, yielding the probability that an electron leaves the system. The procedure is self consistent. Since most photoemission experiments use relatively thick films, the infinite half space is used here. weakest. As a surface-mode is strongly localized in the surface, whereas the bulk-mode is extended throughout the film, the type of plasmon can be determined from the shape of the induced density. This determination may become ambiguous in the vicinity of level crossing, and additional information can be obtained from the asymptotic current, the shape of which does not change, when one follows a particular dispersion. In the second part we use a simple classical approach in order to examine the differences to the above microscopic theory. Using the dielectric function from the Drude model - which permits calculation of analytical results for the resonance positions - the electron energy loss spectrum (EELS) for an electron travelling parallel to the surface is calculated, for a half space and then for a finite film. The classical approach yields only the two surface plasmons and neither the volume nor the multimode modes. The surface mode dispersions coincide with the microscopic ones for very small wavelengths and agree reasonably well otherwise. For this reason, this simple and computationally less demanding scheme is used to determine the dependence of dispersion on film thickness, distance between electron and surface, and electron velocity. The models developed in the first two parts cannot be used for photoemission - an important experimental probe for surface modes - because it is formulated in terms of scalar electron density. In the final part, therefore, Maxwell's In this work, collective modes and induced currents in films of simple metals are calculated, with emphasis on the surface effects. In the first part we use a fully microscopic approach within the theory of Correlated Basis Functions together with the Fermi Hypernetted Chain theory. Introducing an effective potential one is able to transform the equations of motion into equations of a time-dependent Hartree-Fock type. The effective potential accounts for both correlation and exchange effects. The latter are included in a way that is tailored in such a way that the static structure factor calculated is the same as the exact exchange potential. Thin metal films possess a number of collective excitations (plasmons), namely the bulk plasmon, surface plasmons and multimodes. We calculate the dispersion relations of all these modes for aluminium, cesium and potassium, and compare them to experiments and other calculations. Additionally, we derive the formulae for the induced current. The importance of this result lies in the fact that the current is a directly measurable quantity, in contrast to the induced density. The results in the asymptotic limit far away from the system are used to describe electron emission induced by electrons passing the system. We find that the asymptotic current (the number of emitted electrons) shows peaks at the energies corresponding to the various plasmons, which are especially pronounced for the surface plasmons, the bulk plasmon being th