International Symposium on (e,2e) Collisions, Double Photoionization and Related Processes
(e,2e) '93

J. Phys. IV France 03 (1993) C6-197-C6-205
DOI: 10.1051/jp4:1993619

Energy dependence of double photoionization in He

N. BERRAH^{1, 2}, F. HEISER¹, R. WEHLITZ¹, J. LEVIN³, S.B. WHITFIELD¹, J. VIEFHAUS¹, I.A. SELLIN⁴ and U. BECKER<sup>1

1</sup>  Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany
²  Western Michigan University, Physics Department, Kalamazoo, MI 49009, U.S.A.
³  National Institute of Standards and Technology, Gaithersburg, MD 20899, U.S.A.
⁴  University of Tennessee, Physics Department, Knoxville, TN 37996 and Oak Ridge National Laboratory, Oak Ridge, TN 37891, U.S.A.

Abstract
The ratio of double-to-single ionization of He has been measured between 280 eV and 1210 eV to investigate its energy dependence in the intermediate region. The new intermediate energy measurement, compared with the most recent theories of Pan and Kelly and of Hino and Hino et al., show the importance of including not only ground state but also final state correlations. They also appear to indicate the importance of including higher-order effects in the theory. The previously reported [11, 22] high energy measurements between 2-12 keV give a ratio of 1.5 (2)% in good agreement with older shake calculations of Byron and Joachain and of Åberg, as well as with recent many-body perturbation theory of Ishihara et al., calculations of Dalgarno and Sadeghpour, and of Andersson and Burgdörfer. In contrast to the intermediate energy behavior, consideration of final state correlations proves inessential as discussed by Dalgarno and Sadeghpour.

© EDP Sciences 1993