Comment on the form of the x-ray photoemission singularity away from threshold

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Abstract
The deep-hold spectral density as measured by x-ray photoemission is discussed theoretically, expanding on the earlier work of Minnhagen. Strong evidence is presented that the fractional power law which becomes exact asymptotically near threshold, is approximately valid away from threshold as well. This result does not contradict the results of recent numerical calculations, because the Nozières-de Dominicis model Hamiltonian used in these calculations turns out not to be a good approximation away from threshold. Our results are roughly independent of the form assumed for the deep-hole potential.