A New Approach to the Theory of Photoemission from Solids

By neglecting certain terms in the Hamiltonian (of importance only in the immediate neighbourhood of the threshold energy) we are able to write an exact expression for the photoemission intensity which involves the standard time inverted LEED state and broadened hole-states. If inelastic extrinsic losses are neglected our expression is similar to the one used by e.g. Feibelman and Eastman [1], Pendry [2] and Spanjaard et al. [3]. Our theory also allows inelastic losses (including interference between intrinsic and extrinsic losses) to be evaluated. The expressions are similar to those obtained by Inglesfield [4], but the damping effect no longer has to be put in by hand. Our theory further can handle not only core electron but also valence electron photoemission and it is not restricted to metals but applies to all types of solids. We have also traced why and when Inglesfield's one step theory agrees with a semiclassical calculation