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Title: Two-step single-ionization mechanisms

Abstract

In a recent publication [Phys. Rev. Lett. 92, 233202 (2004)] two different electron impact double ionization (e,3e) mechanisms were identified and the way in which two-electron momentum distributions for atoms and molecules could be obtained by triple coincidence (e,3e) measurements was discussed. The apparatus used detected the two ejected electrons both in and out of the scattering plane at an angle of 45 deg. to the momentum transfer direction in triple coincidence with the scattered electron. Ejected electrons detected out of the scattering plane were shown to be a result of two-step double ionization processes. With the same apparatus we have made double coincidence (e,2e) measurements of electron impact single ionization cross sections for ionization of magnesium 3s (valence) and 2p and 2s (inner) shell electrons at incident energies from 400 to 3000 eV in order to obtain more information about two-step ionization. The experimental results were compared with distorted-wave and plane-wave Born approximations carried out to second order. For the experimental conditions, two-step ionization processes involving one ionizing collision and a second elastic collision with the atomic core are the dominant contribution to the measured cross sections. Calculations are in moderate agreement with the data. The angular distributions ofmore » the ionized electrons in these two-step ionizations reflect the initial momentum distributions of the target electrons, a result that is analogous with the earlier (e,3e) measurements.« less

Authors:
;  [1];  [2]; ;  [3];  [4]
  1. Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218 (United States)
  2. Institute for Molecular Science, Okazaki 444-8585 (Japan)
  3. Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742 (United States)
  4. Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742 (United States)
Publication Date:
OSTI Identifier:
20786909
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 73; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevA.73.032703; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ANGULAR DISTRIBUTION; ATOMS; BORN APPROXIMATION; CROSS SECTIONS; DISTORTED WAVE THEORY; ELECTRON-ATOM COLLISIONS; ELECTRONS; EV RANGE; INNER-SHELL IONIZATION; MAGNESIUM; MOLECULES; MOMENTUM TRANSFER; SCATTERING; VALENCE

Citation Formats

Boeyen, R. W. van, Doering, J. P., Watanabe, N., Cooper, J. W., Coplan, M. A., and Moore, J. H. Two-step single-ionization mechanisms. United States: N. p., 2006. Web. doi:10.1103/PHYSREVA.73.0.
Boeyen, R. W. van, Doering, J. P., Watanabe, N., Cooper, J. W., Coplan, M. A., & Moore, J. H. Two-step single-ionization mechanisms. United States. doi:10.1103/PHYSREVA.73.0.
Boeyen, R. W. van, Doering, J. P., Watanabe, N., Cooper, J. W., Coplan, M. A., and Moore, J. H. Wed . "Two-step single-ionization mechanisms". United States. doi:10.1103/PHYSREVA.73.0.
@article{osti_20786909,
title = {Two-step single-ionization mechanisms},
author = {Boeyen, R. W. van and Doering, J. P. and Watanabe, N. and Cooper, J. W. and Coplan, M. A. and Moore, J. H.},
abstractNote = {In a recent publication [Phys. Rev. Lett. 92, 233202 (2004)] two different electron impact double ionization (e,3e) mechanisms were identified and the way in which two-electron momentum distributions for atoms and molecules could be obtained by triple coincidence (e,3e) measurements was discussed. The apparatus used detected the two ejected electrons both in and out of the scattering plane at an angle of 45 deg. to the momentum transfer direction in triple coincidence with the scattered electron. Ejected electrons detected out of the scattering plane were shown to be a result of two-step double ionization processes. With the same apparatus we have made double coincidence (e,2e) measurements of electron impact single ionization cross sections for ionization of magnesium 3s (valence) and 2p and 2s (inner) shell electrons at incident energies from 400 to 3000 eV in order to obtain more information about two-step ionization. The experimental results were compared with distorted-wave and plane-wave Born approximations carried out to second order. For the experimental conditions, two-step ionization processes involving one ionizing collision and a second elastic collision with the atomic core are the dominant contribution to the measured cross sections. Calculations are in moderate agreement with the data. The angular distributions of the ionized electrons in these two-step ionizations reflect the initial momentum distributions of the target electrons, a result that is analogous with the earlier (e,3e) measurements.},
doi = {10.1103/PHYSREVA.73.0},
journal = {Physical Review. A},
number = 3,
volume = 73,
place = {United States},
year = {Wed Mar 15 00:00:00 EST 2006},
month = {Wed Mar 15 00:00:00 EST 2006}
}
  • An electron momentum spectroscopy study on ionization-excitation processes of He is reported. The symmetric noncoplanar (e,2e) cross sections for transitions to excited ion states have been measured relative to that to the ground ion state at impact energies of 1240 and 4260 eV. The experimental results exhibit a marked dependence on the impact energy. This provides strong evidence that higher-order effects are involved. Second-Born-approximation calculations are performed and their results are compared with the experimental ones. It is shown that the two-step mechanisms play crucial roles in the ionization-excitation processes.
  • Ytterbium enriched in {sup 176}Yb is used for the production of the {sup 177}Lu radioisotope, which has applications in cancer treatment. We have theoretically studied the two-step resonant, three-step photoionization of the {sup 176}Yb isotope using the density-matrix approach. To simulate experimentally realistic conditions, the Doppler averaging, magnetic sublevel degeneracy, time-varying Rabi frequencies, ionization rate, angular divergence, and laser bandwidth have all been incorporated into the theoretical model. Calculations have been carried out to identify the optimized Rabi frequencies for evaluating the separation factor. The effect of the laser line shape on the excitation profile has also been thoroughly studied.more » We could obtain large separation factors of {approx}5000 for the {sup 176}Yb isotope, and the excitation conditions identified in this work may be utilized in the separation of the desired isotope.« less
  • The in-gas laser ionization and spectroscopy technique has been developed at the Leuven isotope separator on-line facility for the production and in-source laser spectroscopy studies of short-lived radioactive isotopes. In this article, results from a study to identify efficient optical schemes for the two-step resonance laser ionization of 18 elements are presented.
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