Nondipole Effects in Double Photoionization of He

Authors

A.Y. Istomin, University of Nebraska - Lincoln
N. L. Manakov, Voronezh State UniversityFollow
A. V. Meremianin, Voronezh State UniversityFollow
Anthony F. Starace, University of Nebraska-LincolnFollow

Date of this Version

11-9-2006

Comments

Published by American Institute of Physics; CP811 Ionization, Correlation, and Polarization in Atomic Collisions, edited by A. Lahmam-Bennani and B. Lohmann 0 2006 American Institute of Physics 0-7354-0303-11061$23.00.

Abstract

Lowest-order nondipole effects are studied in double photoionization (DPI) of the He atom. Ah initio parametrizations of the quadrupole transition amplitude for DPI from the ¹S₀state are presented in terms of the exact two-electron reduced matrix elements. Parametrizations for the dipole-quadrupole triply differential cross section (TDCS) and doubly differential cross section (DDCS) are presented in terms of polarization-independent amplitudes for the case of an elliptically polarized photon. Expressions for the DDCS in terms of the reduced two-electron matrix elements are also given. A general analysis of retardation-induced asymmetries of the TDCS including the circular dichroism effect at equal energy sharing is presented. Our numerical results exhibit a nondipole forward-backward asymmetry in the TDCS for DPI of He at an excess energy of 450 eV that is in qualitative agreement with existing experimental data.