We introduce an analytic approximation for the spectral function, which describes the final-state electron-electron interaction in the nonresonant inelastic x-ray scattering process. We show that a relatively simple expression is adequate to characterize the excited state. We have evaluated the spectral function for various free electron densities and momentum transfer values and discuss the final state effects in the light of some recent high resolution Compton scattering experiments. It is shown that the observed smearing of the Fermi edge at relatively low incident photon energies can mostly be associated to the final state effects due to the finite width of the spectral function.

• Received 24 April 2001

DOI:https://doi.org/10.1103/PhysRevB.64.125116