MANY-PARTICLE EFFECTS AT CORE THRESHOLDS IN SIMPLE METALS

We have analyzed inelastic electron-scattering (IES) data at the Na L2,3 and K M2,3 thresholds in terms of the Mahan-NozièresDe Dominicis (MND) model. We have also obtained the absorption coefficient and imaginary dielectric function 2 from the IES data and analyzed them in the same manner as the raw data. For K the peaking parameter ±0 obtained from absorption depends upon whether IES data, , or 2 is used. For Na, ±0 does not vary significantly among the three absorption spectral functions and has a value of 0.22±0.03 if uncertainties in the transition density of states are included. Exchange mixing is found to be a small effect at the Na L2,3 absorption edge. We have reanalyzed published p-core soft-x-ray emission data from Na and K and account for the effects of partial phonon relaxation on ±0. In both cases ±0 is significantly less than for the corresponding absorption spectra with values of about 0.15. We have also reanalyzed published Na core-level x-ray photoemission spectroscopy data including surface contributions and for the appropriate exponent obtain ±=0.22±0.02. The results above taken in concert indicate a failure in the presently accepted MND model. We suggest that previously unconsidered dynamical effects must be included. © 1990 The American Physical Society.