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Title: New developments for an electron impact (e,2e)/(e,3e) spectrometer with multiangle collection and multicoincidence detection

Abstract

We describe new developments aimed to extend the capabilities and the sensitivity of the (e,2e)/(e,3e) multicoincidence spectrometer at Orsay University [Duguet et al., Rev. Sci. Instrum. 69, 3524 (1998)]. The spectrometer has been improved by the addition of a third multiangle detection channel for the fast ''scattered'' electron. The present system is unique in that it is the only system which combines three toroidal analyzers all equipped with position sensitive detectors, thus allowing the triple coincidence detection of the three electrons present in the final state of an electron impact double ionization process. The setup allows measurement of the angular and energy distributions of the ejected electrons over almost the totality of the collision plane as well as that of the scattered electron over a large range of scattering angles in the forward direction. The resulting gain in sensitivity ({approx}25) has rendered feasible a whole class of experiments which could not be otherwise envisaged. The setup is described with a special emphasis on the new toroidal analyzer, data acquisition hardware, and data analysis procedures. The performances are illustrated by selected results of (e,2e) and (e,3e) experiments on the rare gases.

Authors:
; ; ; ; ; ; ;  [1];  [2];  [3]
  1. Laboratoire des Collisions Atomiques et Moleculaires (UMR 8625) and Federation Lumiere Matiere (FR 2764), Batiment 351, Universite de Paris-Sud XI, 91405 Orsay Cedex (France)
  2. (Australia)
  3. (Italy)
Publication Date:
OSTI Identifier:
20953229
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 78; Journal Issue: 1; Other Information: DOI: 10.1063/1.2428275; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; DATA ACQUISITION; DATA ANALYSIS; DETECTION; ELECTRON SPECTROMETERS; ELECTRONS; ENERGY SPECTRA; GAIN; IONIZATION; PERFORMANCE; POSITION SENSITIVE DETECTORS; RARE GASES; SCATTERING; SENSITIVITY

Citation Formats

Catoire, F., Staicu-Casagrande, E. M., Lahmam-Bennani, A., Duguet, A., Naja, A., Ren, X. G., Lohmann, B., Avaldi, L., Centre for Quantum Dynamics, Griffith University, Nathan Qld 4111, and CNR-Istituto di Metodologie Inorganiche e dei Plasmi, Area della Ricerca di Roma 1, CP10, 00016 Monterotondo Scalo. New developments for an electron impact (e,2e)/(e,3e) spectrometer with multiangle collection and multicoincidence detection. United States: N. p., 2007. Web. doi:10.1063/1.2428275.
Catoire, F., Staicu-Casagrande, E. M., Lahmam-Bennani, A., Duguet, A., Naja, A., Ren, X. G., Lohmann, B., Avaldi, L., Centre for Quantum Dynamics, Griffith University, Nathan Qld 4111, & CNR-Istituto di Metodologie Inorganiche e dei Plasmi, Area della Ricerca di Roma 1, CP10, 00016 Monterotondo Scalo. New developments for an electron impact (e,2e)/(e,3e) spectrometer with multiangle collection and multicoincidence detection. United States. doi:10.1063/1.2428275.
Catoire, F., Staicu-Casagrande, E. M., Lahmam-Bennani, A., Duguet, A., Naja, A., Ren, X. G., Lohmann, B., Avaldi, L., Centre for Quantum Dynamics, Griffith University, Nathan Qld 4111, and CNR-Istituto di Metodologie Inorganiche e dei Plasmi, Area della Ricerca di Roma 1, CP10, 00016 Monterotondo Scalo. Mon . "New developments for an electron impact (e,2e)/(e,3e) spectrometer with multiangle collection and multicoincidence detection". United States. doi:10.1063/1.2428275.
@article{osti_20953229,
title = {New developments for an electron impact (e,2e)/(e,3e) spectrometer with multiangle collection and multicoincidence detection},
author = {Catoire, F. and Staicu-Casagrande, E. M. and Lahmam-Bennani, A. and Duguet, A. and Naja, A. and Ren, X. G. and Lohmann, B. and Avaldi, L. and Centre for Quantum Dynamics, Griffith University, Nathan Qld 4111 and CNR-Istituto di Metodologie Inorganiche e dei Plasmi, Area della Ricerca di Roma 1, CP10, 00016 Monterotondo Scalo},
abstractNote = {We describe new developments aimed to extend the capabilities and the sensitivity of the (e,2e)/(e,3e) multicoincidence spectrometer at Orsay University [Duguet et al., Rev. Sci. Instrum. 69, 3524 (1998)]. The spectrometer has been improved by the addition of a third multiangle detection channel for the fast ''scattered'' electron. The present system is unique in that it is the only system which combines three toroidal analyzers all equipped with position sensitive detectors, thus allowing the triple coincidence detection of the three electrons present in the final state of an electron impact double ionization process. The setup allows measurement of the angular and energy distributions of the ejected electrons over almost the totality of the collision plane as well as that of the scattered electron over a large range of scattering angles in the forward direction. The resulting gain in sensitivity ({approx}25) has rendered feasible a whole class of experiments which could not be otherwise envisaged. The setup is described with a special emphasis on the new toroidal analyzer, data acquisition hardware, and data analysis procedures. The performances are illustrated by selected results of (e,2e) and (e,3e) experiments on the rare gases.},
doi = {10.1063/1.2428275},
journal = {Review of Scientific Instruments},
number = 1,
volume = 78,
place = {United States},
year = {Mon Jan 15 00:00:00 EST 2007},
month = {Mon Jan 15 00:00:00 EST 2007}
}
  • The authors have calculated fivefold differential cross sections for double photoionization and eightfold differential cross sections for double ionization by electron impact of helium and alkaline earth atoms for energies of the ionized electrons ranging from a few eV up to 100 eV. Calculations have been done in first Born approximation, using well-converged CI wave functions to describe the initial state, and final state wave functions incorporating the correlation factor used by Brauner, Briggs, and Klar. The angular distributions of the ionized electrons will be discussed. The characteristics of these angular distributions will be analyzed in terms of the partialmore » waves that contribute most strongly to the double ionization processes.« less
  • Double ionization of He by electrons and photons is used to determine the He ground state wave function.
  • The first absolute (e,3e) measurements, by Lahmam-Bennani et al. [Phys. Rev. A 59, 3548 (1999)], have been recently approximately reproduced by Berakdar [Phys. Rev. Lett. 85, 4036 (2000)] and supported by Jones and Madison [Phys. Rev. Lett. 91, 073201 (2003)], but with widely differing conclusions. The former indirectly implied that the Born-CCC-based calculations of Kheifets et al. [J. Phys. B 32, 5047 (1999)] were inaccurate due to the reliance on the first Born approximation. The latter argued that the first Born approximation was valid, but an insufficiently accurate initial state was used. We investigate these claims by performing calculations withmore » ground states similar to those used by Jones and Madison, as well as including the second Born terms. We find the effect of the second Born terms to be negligible and that the original calculations of Kheifets et al. are reproduced if a ground state similar to that of Jones and Madison is used, but appropriately corrected as done by Le Sech and co-workers [J. Phys. B 23, L739 (1990)].« less
  • A high sensitivity and high resolution (e, 2e) electron momentum spectrometer with simultaneous detection in energy and momentum are constructed. The design and performance of the spectrometer are reported. The orbital electron density distributions are obtained accurately and rapidly by using this spectrometer equipped with a double toroidal analyzer. The experimental results on argon and helium exhibit the significant improvements in coincidence count rates, resolution, sensitivity and obtainment of a wide range of adjustable experimental impact energies, which are crucial for further electron momentum spectroscopy studying electronic structure and electron correlation in complex systems.
  • An electron-pair coincidence spectrometer, using only a single electrostatic toroidal analyzer, has been developed for the study of final-state electron pairs following ionization by electron impact. The system allows the angular and energy distribution of electron pairs emitted in a selected plane to be detected by a single planar microchannel plate stack followed by two position-sensitive semicircular wedge-and-strip anodes. The output signals are decoded into energy, angle and nanosecond coincidence timing information from which relative energy and angular triple differential ionization cross sections are determined. The performance of the instrument is indicated by He I photoionization of krypton and themore » first measurements of differential cross sections for electron-impact ionization of the {sup 2}P{sub 3/2} and {sup 2}P{sub 1/}2 states of krypton. For perpendicular-plane scattering and an excess energy of 10 eV for the {sup 2}P{sub 3/2} state and 0.67 eV less for the {sup 2}P{sub 1/2} state, these cross sections are significantly different for the two states and indicate the importance of the final state of the ion in the scattering process.« less