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Title: Nondipole Effects in Double Photoionization of He

Abstract

Lowest-order nondipole effects are studied in double photoionization (DPI) of the He atom. Ab initio parametrizations of the quadrupole transition amplitude for DPI from the 1S0-state 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.

Authors:
;  [1]; ;  [2]
  1. Department of Physics and Astronomy, University of Nebraska, Lincoln, NE 68588-0111 (United States)
  2. Physics Department, Voronezh State University, Voronezh 394006 (Russian Federation)
Publication Date:
OSTI Identifier:
20797872
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 811; Journal Issue: 1; Conference: International symposium on (e,2e) double photoionization, and related topics; 13. international symposium on polarization and correlation in electronic and atomic collisions, Buenos Aires (Argentina), 28-30 Jul 2005; Other Information: DOI: 10.1063/1.2165614; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ASYMMETRY; DICHROISM; DIFFERENTIAL CROSS SECTIONS; DIPOLES; ELECTRONS; ENERGY LEVELS; EV RANGE; HELIUM; MATRIX ELEMENTS; PHOTOIONIZATION; PHOTONS; POLARIZATION; QUADRUPOLES; TRANSITION AMPLITUDES

Citation Formats

Istomin, A. Y., Starace, A. F., Manakov, N. L., and Meremianin, A. V. Nondipole Effects in Double Photoionization of He. United States: N. p., 2006. Web. doi:10.1063/1.2165614.
Istomin, A. Y., Starace, A. F., Manakov, N. L., & Meremianin, A. V. Nondipole Effects in Double Photoionization of He. United States. doi:10.1063/1.2165614.
Istomin, A. Y., Starace, A. F., Manakov, N. L., and Meremianin, A. V. Mon . "Nondipole Effects in Double Photoionization of He". United States. doi:10.1063/1.2165614.
@article{osti_20797872,
title = {Nondipole Effects in Double Photoionization of He},
author = {Istomin, A. Y. and Starace, A. F. and Manakov, N. L. and Meremianin, A. V.},
abstractNote = {Lowest-order nondipole effects are studied in double photoionization (DPI) of the He atom. Ab initio parametrizations of the quadrupole transition amplitude for DPI from the 1S0-state 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.},
doi = {10.1063/1.2165614},
journal = {AIP Conference Proceedings},
number = 1,
volume = 811,
place = {United States},
year = {Mon Jan 09 00:00:00 EST 2006},
month = {Mon Jan 09 00:00:00 EST 2006}
}
  • Lowest-order nondipole effects are studied systematically in double photoionization (DPI) of the He atom. Ab initio parametrizations of the quadrupole transition amplitude for DPI from the {sup 1}S{sub 0} state are presented in terms of the exact two-electron radial matrix elements. Analytic expressions for these matrix elements within lowest-order perturbation theory (LOPT) in the interelectron interaction are also given. The corresponding parametrizations for the dipole-quadrupole triply differential cross section (TDCS) are presented for the case of an elliptically polarized photon. A general analysis of retardation-induced asymmetries of the TDCS including the circular dichroism effect at equal energy sharing is presented.more » Numerical LOPT estimates of nondipole asymmetries in photoelectron angular distributions for the cases of linear and circular polarization and of the circular dichroism effect at equal energy sharing are presented. We find that experimental observation of nondipole effects at excess energies of the order of tens to hundreds of eV should be feasible in TDCS measurements. 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.« less
  • Similarly to differential cross sections for one-electron photoionization, the doubly differential cross section for double photoionization (DPI) may be conveniently described by four parameters: the singly differential (with respect to energy sharing) cross section ({sigma}{sub 0}), the dipole asymmetry parameter ({beta}), and two nondipole asymmetry parameters ({gamma} and {delta}). Here we derive two model-independent representations for these parameters for DPI from a {sup 1}S{sub 0} atomic bound state: (i) in terms of one-dimensional integrals of the polarization-invariant DPI amplitudes and (ii) in terms of the exact two-electron reduced matrix elements. For DPI of He at excess energies, E{sub exc}, ofmore » 100 eV, 450 eV, and 1 keV, we present numerical results for the asymmetry parameters within the framework of the convergent close-coupling theory and compare them with results of lowest-order (in the interelectron interaction) perturbation theory (LOPT). The results for E{sub exc}=1 keV exhibit a nondipole asymmetry that is large enough to be easily measured experimentally. We find excellent agreement between our LOPT results and other theoretical predictions and experimental data for total cross sections and ratios of double to single ionization cross sections for K-shell DPI from several multielectron atoms.« less
  • The parameter that determines the nondipole correction to the angular distribution is calculated for Ar 1s and 3s subshells in the Hartree-Fock (HF) approximation and taking account of the multielectron correlations, using the random-phase approximation with exchange. In the photoelectron energy range 0{endash}100 eV the parameter, which for {ital s} subshells is nonzero at threshold, is found for Ar 3s to be strongly affected by multielectron correlations. Results are also presented for He and Be in the HF approximation. thinsp {copyright} {ital 1999} {ital The American Physical Society}
  • The random-phase approximation (RPA) is applied to study nondipole corrections to the angular distribution of photoelectrons from the n=2 shell of Ne. Calculations of the parameters {gamma}{sub nl} and {delta}{sub nl} arising from E{sub 1}-E{sub 2} interference effects are carried out for the 2s and 2p subshells of Ne in the photon energy range 100{endash}2000 eV. For the 2s shell, the RPA calculations show small effects of correlation near the 2s threshold energy, but are otherwise in agreement with independent-particle approximation (IPA) calculations. The RPA and IPA values of {gamma}{sub 2s} are also in agreement with experiment. For the 2pmore » shell, a small difference between RPA and IPA calculations of the nondipole parameters is found for energies near the 1s threshold; however, both RPA and IPA calculations of the parameter {gamma}{sub 2p}+3{delta}{sub 2p} disagree significantly with experimental measurements for photon energies above 1000 eV. thinsp {copyright} {ital 1999} {ital The American Physical Society}« less
  • Strong evidence for the existence and importance of quadrupole satellite transitions is found in spin-orbit-resolved Xe 4d nondipole photoionization in a combined experimental/theoretical study.