ONE-STEP MODEL OF PHOTOEMISSION FOR NONLOCAL POTENTIALS

The one-step model of valence-band photoemission and inverse photoemis sion from single-crystal surfaces is reformulated for generalized (non local, complex and energy-dependent) potentials. Thereby, it becomes p ossible to account for self-energy corrections taken from many-body el ectronic-structure calculations. The original formulation due to Pendr y and coworkers employs the KKR multiple-scattering theory for the cal culation of the initial state. This prevents a straightforward general ization of the one-step model to nonlocal potentials. We therefore con sider the Dyson equation which is set up within a muffin-tin-orbital r epresentation as an alternative to obtain the initial-state Green func tion. This approach requires a revision of the transition-matrix eleme nts which is carried out in detail. The final state is considered as a time-reversed LEED state as usual. The proposed generalization of the one-step model allows to distinguish between the bare photocurrent re flecting the (quasi-particle) band structure and the secondary effects due to the (dipole) selection rules and due to the wave-vector and en ergy dependence of the transition-matrix elements.