Theoretical description of spin-resolved appearance potential spectroscopy

A theoretical description of spin-resolved appearance potential spectroscopy is presented on the basis of a single-particle description of the underlying electronic structure. The final expression for the signal intensity turns out to be essentially a cross-section-weighted self-convolution of the density of states above the Fermi energy, in close analogy to the result for core-valence-valence Auger electron spectroscopy. Application of the formalism presented to bcc Fe and fcc Ni leads to results in very satisfying agreement with corresponding experimental data. Because this is achieved only by treating the involved transition matrix elements in a proper way, their properties are discussed in some detail.