Photoelectron-diffraction effects and circular dichroism in core-level photoemission

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Abstract
We have calculated the circular dichroism associated with core-level photoemission using multiple-scattering photoelectron-diffraction theory. For C 1s emission in a chiral geometry from CO adsorbed on Pd(111), photoelectron-diffraction calculations predict the dichroism found in experimental results due to Bansmann et al. and also agree well with prior free-molecule calculations by McKoy and Stephens. Backscattering from the Pd substrate is also found to alter the dichroic asymmetries for different adsorption geometries. Analogous calculations for Fe 2p emission from a small Fe cluster also indicate that dichroism due to a chiral geometry can strongly affect measurements of magnetic circular dichroism in systems with net magnetization. With generalization to include spin-orbit and multiplet splittings in the initial state and spin-dependent scattering of the outgoing electrons, photoelectron-diffraction theory thus should provide a general method for modeling dischroism in core-level photoemission from both nonmagnetic and magnetic systems.