Madelung Potentials and Disorder Broadening of Core Photoemission Spectra in Random Alloys

We present the first experimental evidence for ``disorder broadening'' of core level x-ray photoemission line shapes in alloys. The broadening is attributed to variations in electrostatic potential. A model in which the charge on a site is assumed to be proportional to its number of unlike neighbors has recently been shown to greatly improve the calculated total energies of disordered alloys. This model predicts a broadening a factor of 2 larger than observed. We discuss this result in terms of short range order and a generalized charge model.