Near threshold behavior of Rayleigh scattering

Abstract

We discuss problems in recognizing the physically observable aspects of calculated structures in near-threshold Rayleigh scattering. Various structures in near-threshold photoionization, and irregularities in the ionic cross sections across isonuclear sequences, are understood to be unphysical. These structures are associated with the lack of smoothness in Latter-tail potentials or over-screening of inner electrons in potentials which allow these electrons to see their own charge distributions. Such problems are remedied as one goes beyond independent particle approximation (IPA) potentials or at the IPA level by using "vacancy potentials"; we find in photoionization this leads to improved agreement with experiment. In this work Rayleigh scattering cross sections for neutral neon and argon have also been calculated using such vacancy potentials for photon energies near threshold, but requiring experimental threshold energies.