Interpretation of the soft X-ray emission spectrum of lithium metal

The shape of the soft X-ray emission spectrum of lithium has been calculated in the Hartree-Fock approximation taking into account the fact that an atom about to emit a K X-ray is a point defect in the otherwise periodic potential of the lattice. The perturbation from the 1s hole was treated in the `localized approximation' of the Koster-Slater theory, its effect being expressed by a single parameter. Starting from Ham's calculated density-of-states function and gradually increasing the strength of the perturbation one observes the formation of a resonance state (virtual bound state) and then a real bound state. For reasonable values of the perturbation parameter the results show a peak about 1 ev below the Fermi energy, a feature which resembles the measurements of Crisp and Williams and others. The calculations also provide a plausible explanation of the measurements of Catterall and Trotter on the satellite K emission spectrum of lithium.