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Title: Low-energy electron capture by Ne{sup 2+} ions from H(D)

Abstract

Using the Oak Ridge National Laboratory (ORNL) ion-atom merged-beams apparatus, the absolute, total single-electron-capture cross section has been measured for collisions of Ne{sup 2+} with deuterium (D) at center-of-mass (c.m.) collision energies of 59-949 eV/u. With the high-velocity ion beams now available at the ORNL Multicharged Ion Research Facility, we have extended our previous merged-beams measurement to lower c.m. collision energies. The data are compared to all four previously published measurements for Ne{sup 2+}+H(D) which differ considerably from one another at energies (less-or-similar sign)600 eV/u. We are unaware of any published theoretical cross-section data for Ne{sup 2+}+H(D) at the energies studied. Early quantal rate coefficient calculations for Ne{sup 2+}+H at eV/u energies suggest a cross section many orders of magnitude below previous measurements of the cross section at 40 eV/u which is the lowest collision energy for which experimental results have been published. Here we compare our measurements to recent theoretical electron-capture results for He{sup 2+}+H. Both the experimental and theoretical results show a decreasing cross section with decreasing energy.

Authors:
; ; ; ; ; ;  [1];  [2];  [2]
  1. Columbia Astrophysics Laboratory, Columbia University, New York, New York 10027-6601 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
20982605
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 75; Journal Issue: 5; Other Information: DOI: 10.1103/PhysRevA.75.054701; (c) 2007 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; ATOMS; CATIONS; CENTER-OF-MASS SYSTEM; COMPARATIVE EVALUATIONS; CROSS SECTIONS; DEUTERIUM; ELECTRON CAPTURE; EV RANGE; HYDROGEN; ION BEAMS; ION-ATOM COLLISIONS; MULTICHARGED IONS; NEON IONS; ORNL; TOTAL CROSS SECTIONS; VELOCITY

Citation Formats

Seredyuk, B., Bruhns, H., Savin, D. W., Seely, D., Aliabadi, H., Galutschek, E., Havener, C. C., Albion College, Department of Physics, Albion, Michigan 49224-1831, and Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6372. Low-energy electron capture by Ne{sup 2+} ions from H(D). United States: N. p., 2007. Web. doi:10.1103/PHYSREVA.75.054701.
Seredyuk, B., Bruhns, H., Savin, D. W., Seely, D., Aliabadi, H., Galutschek, E., Havener, C. C., Albion College, Department of Physics, Albion, Michigan 49224-1831, & Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6372. Low-energy electron capture by Ne{sup 2+} ions from H(D). United States. doi:10.1103/PHYSREVA.75.054701.
Seredyuk, B., Bruhns, H., Savin, D. W., Seely, D., Aliabadi, H., Galutschek, E., Havener, C. C., Albion College, Department of Physics, Albion, Michigan 49224-1831, and Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6372. Tue . "Low-energy electron capture by Ne{sup 2+} ions from H(D)". United States. doi:10.1103/PHYSREVA.75.054701.
@article{osti_20982605,
title = {Low-energy electron capture by Ne{sup 2+} ions from H(D)},
author = {Seredyuk, B. and Bruhns, H. and Savin, D. W. and Seely, D. and Aliabadi, H. and Galutschek, E. and Havener, C. C. and Albion College, Department of Physics, Albion, Michigan 49224-1831 and Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6372},
abstractNote = {Using the Oak Ridge National Laboratory (ORNL) ion-atom merged-beams apparatus, the absolute, total single-electron-capture cross section has been measured for collisions of Ne{sup 2+} with deuterium (D) at center-of-mass (c.m.) collision energies of 59-949 eV/u. With the high-velocity ion beams now available at the ORNL Multicharged Ion Research Facility, we have extended our previous merged-beams measurement to lower c.m. collision energies. The data are compared to all four previously published measurements for Ne{sup 2+}+H(D) which differ considerably from one another at energies (less-or-similar sign)600 eV/u. We are unaware of any published theoretical cross-section data for Ne{sup 2+}+H(D) at the energies studied. Early quantal rate coefficient calculations for Ne{sup 2+}+H at eV/u energies suggest a cross section many orders of magnitude below previous measurements of the cross section at 40 eV/u which is the lowest collision energy for which experimental results have been published. Here we compare our measurements to recent theoretical electron-capture results for He{sup 2+}+H. Both the experimental and theoretical results show a decreasing cross section with decreasing energy.},
doi = {10.1103/PHYSREVA.75.054701},
journal = {Physical Review. A},
number = 5,
volume = 75,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • Relative doubly differential cross sections for Penning ionization in the title systems are reported at a mean collision energy of 10.4 kcal/mol in a crossed supersonic beams experiment. As in paper I of this series on He*(2{sup 1}{ital S})+H,D, the H{sup +},D{sup +} products are scattered sharply forward with respect to the incident H,D in the center-of-mass frame, but with the release of an additional 30 kcal/mol into translational energy at the peak of the distribution. Unlike the results of paper I, we find that a single optical potential, corresponding to an autoionizing state of NeH of assumed {sup 2}{Sigma}{supmore » +} symmetry, consistently represents the main features of both previously reported low-energy Penning ionization electron spectroscopy (PIES) data and the present results. Agreement between theory and experiment in the angular distributions is improved by including coupling between the angular momenta of the Penning electron and the atoms after ionization. The resonance width for PI is found to be nonexponential, showing a saturation'' effect at small distance. This is interpreted in terms of the ionic (charge transfer) character of the bonding in NeH*.« less
  • We have measured the electron emission yields ..gamma.. of clean aluminum under bombardment with H/sup +/, H/sub 2/ /sup +/, D/sup +/, D/sub 2/ /sup +/, He/sup +/, B/sup +/, C/sup +/, N/sup +/, N/sub 2/ /sup +/, O/sup +/, O/sub 2/ /sup +/, F/sup +/, Ne/sup +/, S/sup +/, Cl/sup +/, Ar/sup +/, Kr/sup +/, and Xe/sup +/ in the energy range 1.2--50 keV. The clean surfaces were prepared by in situ evaporation of high-purity Al under ultra-high-vacuum conditions. It is found that kinetic electron emission yields ..gamma../sub k/, obtained after subtracting from the measured ..gamma.. a contribution duemore » to potential emission, are roughly proportional to the electronic stopping powers, for projectiles lighter than Al. For heavier projectiles there is a sizable contribution to electron emission from collisions involving rapidly recoiling target atoms, which increases with the mass of the projectile, and which dominates the threshold and near-threshold behavior of kinetic emission. The results, together with recently reported data on Auger electron emission from ion-bombarded Al show that the mechanism proposed by Parilis and Kishinevskii of inner-shell excitation and subsequent Auger decay is negligible for light ions and probably small for heavy ions on Al and in our energy range. We thus conclude that kinetic electron emission under bombardment by low-energy ions results mainly from the escape of excited valence electrons.« less
  • State selective differential and total cross sections for single-electron capture processes by low-energy Ar{sup q+} (q = 4 - 8) ions from He and Ne targets have been studied experimentally at impact energies between 30 and 100 qeV, and laboratory scattering angles between 0{degrees} and 5{degrees}, by means of translational energy-gain spectroscopy. The ions were produced in a recoil ion source, pumped by a fast beam from the WMU Van de Graaff accelerator. The dominant processes are found to be single-electron capture (SEC) into the excited states of the projectile products. In additional to SEC, transfer excitation processes are alsomore » observed. It is found that the population of the dominant reaction channels is consistent with the predictions of the classical over-barrier model. The multichannel Landau-Zener (MCLZ) model has been used to obtain cross sections for capture into individual states. The MCLZ calculations are shown to be in good agreement with the measured energy-gain spectra. Total cross sections for single-electron capture are compared to the single-crossing Landau-Zener model, classical over-barrier model and available measurements. The general features of the angular distributions are discussed in terms of a semiclassical curve-crossing model.« less
  • Measurements and theoretical analyses of total electron-capture cross sections for collisions of N{sup 4+} with ground-state hydrogen (deuterium) are reported in the energy range 1--300 eV/u. The present measurements have reduced relative uncertainty compared to previous absolute measurements at Oak Ridge National Laboratory [Huq {ital et} {ital al}., Phys. Rev. A 40, 1811 (1989)] and are used for detailed comparison with more recent coupled-channel molecular-orbital calculations [Shimakura {ital et} {ital al}., Phys. Rev. A 45, 267 (1992); Zygelman {ital et} {ital al}., {ital ibid}. 46, 3846 (1992)]. The most striking difference between the calculations was the increasing trend in themore » cross section for collision energies below 4 eV/u, as estimated by Zygelman {ital et} {ital al}. using only singlet states of the quasimolecule and the decreasing trend predicted by Shimakura {ital et} {ital al}. using both singlet and triplet states. The latter decreasing trend is consistent with the previous measurement. At 0.5 eV/u, the predicted singlet cross sections differ nearly by a factor of 2. Possible origins for this difference are explored. Strong structure is predicted in the cross section of Zygelman {ital et} {ital al}. and, to a lesser extent, in that of Shimakura {ital et} {ital al}. ; however, the phase of the structure is different in the two theories. Structures observed in the measurement at the higher collision energies are not in complete harmony with either prediction.« less