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Title: Multielectron Processes in Heavy Ion{endash}Atom Collisions at Intermediate Velocity

Abstract

Using high resolution x-ray spectroscopy, we have measured projectile electron single and multiple cross sections when a two-electron Ar{sup 16+} ion collides with neutral target atoms. For a fixed impact velocity (v{sub p}=23 a.u. ) , but using various targets from He to Xe, a range from the perturbative regime to the strong interaction regime has been investigated. Double excitation cross sections are found to be well reproduced by an independent electron model. First measurements of capture-ionization cross sections are also reported and show the importance of this often-neglected process. {copyright} {ital 1997} {ital The American Physical Society}

Authors:
; ; ;  [1]; ; ; ;  [2];  [3];  [4]
  1. GPS (CNRS UMR 75-88), Universites Paris 7 et 6, 2 Place Jussieu, 75251 Paris Cedex 05 (France)
  2. CIRIL (UMR N11 CEA/CNRS), Rue Claude Bloch, B.P.5133, 14070 Caen Cedex 5 (France)
  3. DARC, Observatoire de Paris Meudon, Place Jansen, 92195 Meudon Cedex (France)
  4. NIM, IPN, Universite Paris 11, B.P.N1, 91405 Orsay Cedex (France)
Publication Date:
OSTI Identifier:
545006
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 79; Journal Issue: 19; Other Information: PBD: Nov 1997
Country of Publication:
United States
Language:
English
Subject:
66 PHYSICS; ION-ATOM COLLISIONS; ARGON IONS; MULTIPLE PRODUCTION; ELECTRONS; VELOCITY; X-RAY SPECTROSCOPY; EXCITATION; CROSS SECTIONS; IONIZATION; CAPTURE

Citation Formats

Vernhet, D., Rozet, J.P., Wohrer, K., Chetioui, A., Adoui, L., Cassimi, A., Grandin, J.P., Ramillon, J.M., Cornille, M., and Stephan, C. Multielectron Processes in Heavy Ion{endash}Atom Collisions at Intermediate Velocity. United States: N. p., 1997. Web. doi:10.1103/PhysRevLett.79.3625.
Vernhet, D., Rozet, J.P., Wohrer, K., Chetioui, A., Adoui, L., Cassimi, A., Grandin, J.P., Ramillon, J.M., Cornille, M., & Stephan, C. Multielectron Processes in Heavy Ion{endash}Atom Collisions at Intermediate Velocity. United States. doi:10.1103/PhysRevLett.79.3625.
Vernhet, D., Rozet, J.P., Wohrer, K., Chetioui, A., Adoui, L., Cassimi, A., Grandin, J.P., Ramillon, J.M., Cornille, M., and Stephan, C. 1997. "Multielectron Processes in Heavy Ion{endash}Atom Collisions at Intermediate Velocity". United States. doi:10.1103/PhysRevLett.79.3625.
@article{osti_545006,
title = {Multielectron Processes in Heavy Ion{endash}Atom Collisions at Intermediate Velocity},
author = {Vernhet, D. and Rozet, J.P. and Wohrer, K. and Chetioui, A. and Adoui, L. and Cassimi, A. and Grandin, J.P. and Ramillon, J.M. and Cornille, M. and Stephan, C.},
abstractNote = {Using high resolution x-ray spectroscopy, we have measured projectile electron single and multiple cross sections when a two-electron Ar{sup 16+} ion collides with neutral target atoms. For a fixed impact velocity (v{sub p}=23 a.u. ) , but using various targets from He to Xe, a range from the perturbative regime to the strong interaction regime has been investigated. Double excitation cross sections are found to be well reproduced by an independent electron model. First measurements of capture-ionization cross sections are also reported and show the importance of this often-neglected process. {copyright} {ital 1997} {ital The American Physical Society}},
doi = {10.1103/PhysRevLett.79.3625},
journal = {Physical Review Letters},
number = 19,
volume = 79,
place = {United States},
year = 1997,
month =
}
  • A new method is described for studying collision dynamics in slow ion/atom{endash}atom collisions. It is a generalization of the single-electron, two-center hidden crossings method to multielectron systems. This approach derives from the analytic properties of energy surfaces and wave functions of the adiabatic electronic Hamiltonian when the internuclear distance is extended into the complex plane. The collision dynamics in the adiabatic limit is determined by the topology of the unique multivalued electronic energy surface, particularly by its singular points, the square-root branch points. The surfaces described here have been studied using a complex version of the unrestricted Hartree{endash}Fock and configurationmore » interaction method with all single electron excitations, based on a bivariational principle. Although various inelastic processes can be calculated, the method is especially useful for the description of ionization. We have illustrated this through the calculation of cross sections for ionization of helium by proton and antiproton impact, as well as for the collision of two hydrogen atoms. {copyright} {ital 1998 American Institute of Physics.}« less
  • Electron capture to the K shell of projectiles from the K and other subshells of multielectron target atoms is studied in the intermediate energy region using the single-active-electron approximation and the two-state, two-center atomic eigenfunction expansion method. It is concluded that the theoretical capture cross section is not sensitive to the atomic models used at high collision energies where the projectile velocity v is near or greater than the orbital velocity v/sub e/ of the active electron. For v
  • We report investigations of one- and two-electron processes in the collisions of 0.9-keV/u to 60-keV/u ([ital v][sub [ital p]]=0.19--1.55 a.u.) Ar[sup 16+] ions with He targets. The cross sections for these processes were measured by observing the final charges of the Ar ions and the recoiling target ions in coincidence. The average [ital Q] values for the capture channels were determined by measuring the longitudinal momenta of the recoiling target ions. Single capture (SC) is the dominant process and is relatively independent of the projectile energy. The two-electron transfer-ionization (TI) process is the next largest and slowly increases with projectilemore » energy. The [ital Q] values for both SC and TI decrease with increasing projectile energy. Our data thereby suggest that electrons are captured into less tightly bound states as the collision velocity is increased. Both double capture and single ionization are much smaller and fairly independent of the projectile energy. The energy independence of SI is somewhat surprising as our energy range spans the region of the target electron velocity where ionization would be expected to increase. Our analysis suggests that the ionization process is being suppressed by SC and TI processes.« less
  • The total electron loss, target ionization, and simultaneous projectile-target ionization are measured for He[sup +] projectiles on H[sub 2] and He in the energy range of 1.5--4.0 MeV. The experimental data are in good agreement with calculations based on the independent-particle model including screening, antiscreening, and target-ionization probabilities as well as second-order mechanisms for the simultaneous projectile-target ionization.
  • The impact-parameter dependence of the inner-shell excitation was measured for 1.4-MeV/u Ni ions on Zr, Ag, Te, and Au. All the measured vacancy-production prob- p abilities have impact-parameter dependences typical for direct excitation. Scaling the impact parameter with the adiabatic radius, calculated using united-atom binding energies, all Ni K data can be brought to one common curve. The impact-parameter region contributing most to the vacancy-production cross section, as well as the plateau value of the vacancy-production probability attained at the lowest impact parameters could be explained by extending the semiclassical-approximation method to these collision systems.