Momentum-Transfer Dependence of theLII,IIIEdge of Mg

Abstract

We report measurements of the $L_{\mathrm{I}\mathrm{I},\mathrm{I}\mathrm{I}\mathrm{I}}$ x-ray threshold in Mg at momentum transfers of $q=0\mathrm{} \mathrm{and} 1.8$ ${\mathrm{\AA }}^{-1\mathrm{}}$. We found that a straightforward application of the theory of Mahan, Nozières, and De Dominicis failed to describe the data. We conclude that for Mg, and probably for all polyvalent metals, other effects are at least as important as this theory for describing absorption threshold shapes.