Recent results for excitonic processes in the spectra of metals and alloys

Over the past year our understanding of optical and other excitation processes which create electron-hole pairs in metals and alloys has been completely revised. It is now clearly established that the Coulomb interaction between the electron and hole carriers freshly created in the optical event plays a major role in determining the response of the metal. This article describes the experimental and theoretical developments which underlie the new understanding of these processes. The new work concerns: (i) shallow excitations in alloys; (ii) excitonic processes which modify interband transitions in pure polyvalent metals and (iii) deep interband transitions which occur in the famous “x-ray edge” problem for metals and alloys.