Resonant coherent excitation of N{sup 6+} and Mg{sup 11+} in planar channeling [electronic resource] : Anisotropies in ionization probabilities and x-ray emission

Published: Washington, D.C. : United States. Dept. of Energy, 1994.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Physical Description: 24 pages : digital, PDF file
Additional Creators: Oak Ridge National Laboratory, United States. Department of Energy, and United States. Department of Energy. Office of Scientific and Technical Information

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Summary

The thrust of the conference in which this paper is presented is toward inelastic interactions of ions with surfaces. The work described in this paper deals with inelastic interactions of ions in planar channeling inside the crystal. The authors are, however, not too far off the mark because the planar channeling potential is made up from the sum of two (sheet) surface potentials. For the nitrogen experiment, a beam of N{sup 6+} ions at an energy of 3.25 MeV/amu was supplied by the ORNL EN Tandem accelerator. After suitable collimation, it was passed through an Au crystal (1,800 Å thick). The emergent charge-state distribution was analyzed by electrostatic deflection followed by a solid-state position-sensitive detector. Charge states 5, 6 and 7 were simultaneously detected. In the case of Mg{sup 11+} the beam was supplied at an energy of 25 MeV/amu by the CSCC Tandem Cyclotron Facility at Chalk River, Canada, and passed through an Ni crystal 4,000 Å thick which was epitaxially grown with the surface parallel to a (100) plane. The beam was charge state analyzed by a Q3D magnetic analyzer in which charges 11+ and 12+ were registered. At the energy in question, almost no 10+ fraction is visible. Two Si(Li) X-ray detectors aimed at 90° and 45° recorded the emission of Mg{sup 11+} Lyα (n = 2 → 1) X-rays. In conclusion, there is strong evidence that once a given ionic state is excited, a large fraction of the ions remain in that state and are either ionized or radiate from that state. The result is counter to the expectation that electron-ion collisions in the channel would have a large enough cross section to destroy the alignment before either of these two events could take place. At this point, the reasons for the observed retention of anisotropy are open to conjecture.

Report Numbers

E 1.99:conf-9408150--3
conf-9408150--3

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Note

Published through SciTech Connect.
12/31/1994.
"conf-9408150--3"
"DE95006732"
""
10. international workshop of inelastic ion-surface collisions,Grand Targhee Resort, WY (United States),8-12 Aug 1994.
Davies, W.G.; Ball, G.S.; Krause, H.F.; Datz, S.; Vane, C.R.; Crawford, O.H.; Forster, J.S.; Geiger, J.S.; Dittner, P.F.

Funding Information

AC05-84OR21400

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