Effects of Initially Excited Hole States on the Soft-X-Ray Emission Spectra of Metals

A general theory of the effects of Coulomb excitation of a deep hole state in a solid on the subsequent soft-x-ray emission line shape is given. For excitation energies well above threshold it is shown that the emission corresponds to the decay of a nonrelaxed initial hole state which is suddenly introduced into the solid. Using a weak-coupling approximation, a generalization of the Weisskopf-Wigner formula for radiative line shapes is derived which includes the enhancement of the high-energy tail of an emission line or edge due to initial excitations. Comparison of the approximate results with measurements of the K edge of Li metal provides a reasonable explanation of the observed discrepancy between absorption and emission line shapes.