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H Schmidt-Böcking,
V Mergel,
R Dörner,
C L Cocke,
O Jagutzki,
L Schmidt,
Th Weber,
H J Lüdde,
E Weigold, J Berakdar,
H Cederquist,
H T Schmidt,
R Schuch,
A S Kheifets
EUROPHYSICS LETTERS Europhys. Lett. 01/2002; 27.
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ABSTRACT: We have performed an experiment in which a polarized electron beam ionizes an orbitally oriented and/or spin-polarized valence electron of sodium. The cross section for this reaction is measured for well-resolved vector momenta of the two electrons in the final channel. In order to study the transfer of the initial spin and orbital orientation from the electron-atom system to the final-state correlated electron pair, we develop a tensorial recoupling scheme in which the measured quantities are expressed in terms of independent, irreducible spherical tensor components. By this procedure the cross section is separated into terms characterized by their specific rotational transformation properties, decoupling of geometrical effects due to initial-state preparation from effects associated with details of the scattering dynamics is achieved, and exchange and orbital angular momentum transfer effects are disentangled. For a comparison with experiment we performed numerical ionization-cross section calculations within the distorted wave Born approximation and the dynamically screened three Coulomb waves theory. For some tensorial parameters significant discrepancies between theory and experiment are observed that underline the importance of the state-specific measurements as stringent tests of scattering theories.
Phys. Rev. A. 09/2001; 64(4).
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ABSTRACT: We present the first measurement of (e,2e) ionization cross sections for a laser oriented atomic target by spin polarized electrons. Cross sections are presented as a function of target orientation and polarization direction of the incident electron beam. This study provides insight into mechanisms by which angular momentum is transferred from the valence electron to the two final-state continuum electrons in both singlet and triplet spin channels, by comparing measurement with distorted wave Born approximation and the dynamically screened three Coulomb wave calculations.
Physical Review Letters 02/2001; 86(4):624-7. · 7.37 Impact Factor
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ABSTRACT: Measurements are reported for kinematically complete electron-impact ionization collisions with oriented 3P sodium atoms excited from the ground state by right- and left-hand circularly polarized light. The measurements reveal a strong dependence of the ionization cross section on the helicity inversion of the exciting photon. This dichroic effect and the magnetic state resolved cross sections are described using the distorted-wave Born approximation and the dynamically screened Coulomb wave method. Within the context of these methods we investigate the role of different short- and long-range interactions involved in the process. For moderate values of incident energy we conclude that the shape and magnitude of the dichroism is predominantly determined by the Coulomb interactions of the outgoing electrons with the residual ion. For slow escaping electrons the dichroism is also influenced by the interelectronic correlations.
Phys. Rev. A. 06/2000; 62(1).
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ABSTRACT: The fully differential cross sections for the electron-impact ionization of atomic targets, prepared in a given circular state using laser-pumping, reveal a dependence on the inversion of the helicity of the exciting photon. This `dichroism' effect was shown to be strongly dependent on the geometrical arrangements of the experiment both theoretically and experimentally. In addition, as shown theoretically in this paper, the dichroism may also vanish at certain `non-geometrical' points that can be deduced analytically within the first Born approximation. More elaborate calculations using the distorted-wave Born approximation confirm this analysis. On the basis of this study, we further suggest a possible explanation for a structure observed recently in the state-resolved fully differential cross sections for a sodium target.
Journal of Physics B Atomic Molecular and Optical Physics 08/1999; 32(15):3965. · 1.88 Impact Factor
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H Schmidt-Böcking,
V Mergel,
R Dörner,
O Jagutzki,
L Schmidt,
T. Weber,
C L Cocke,
H. J. Lüdde,
E. Weigold,
Y. V. Popov,
H Cederquist,
H T Schmidt,
R. Schuch, J. Berakdar
Correlations, Polarization, and Ionization in Atomic Systems, Predeal, Romania, 120-126 (2002).
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Correlations, Polarization, and Ionization in Atomic Systems, 32-37 (2002).
