Atomic information in the characterization of atomic photoionization

We show that atomic photoionization at all energies can be described in terms of nuclear Coulomb properties plus a limited number of atomic Screening parameters. Our results support the conclusion that only screening corrections to the lowest multipoles are needed for photoionization differential cross sections. Quadrupole screening can be important except in the lightest atoms, while octupole screening is important in inner shells of intermediate-Z atoms and in all shells of high-Z atoms. We provide a simple way to predict in what energy ranges and for what ejection angles theta quadrupole and octupole screening effects are greatest. [S1050-2947(98)01712-0].