Dynamical processes at surfaces: Excitation of electron-hole pairs

We study the dynamical response of metal surfaces to external electric fields which vary slowly in space and time. It is shown that a linear response function g(q,) determines the influence of a metal surface on all dynamical processes occurring outside of it. We evaluate g(q,) approximately within the jellium model and compare the result with electron-energy-loss measurements on Cu(100) and Ni(100). Good agreement between theory and experiment is obtained, particularly for Cu(100). Finally, we give illustrative applications to the frictional force on a charged particle and the damping of excitations at surfaces. © 1984 The American Physical Society.