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Title: High-Precision Cross Sections for Low-Energy Electron-Atom Collisions

Abstract

We describe a recently developed B-spline R-matrix method for electron and photon collisions with atoms and ions. Using non-orthogonal sets of orbitals to construct the target description and to represent the scattering functions, this implementation of the close-coupling approach allows us to employ highly correlated target wavefunctions with relatively small configuration expansions. Example results from recent applications of the method for accurate calculations of low-energy electron scattering from He, Zn, Ne, Ar, Xe, and Fe+ are presented.

Authors:
;  [1]
  1. Department of Physics and Astronomy, Drake University, Des Moines, Iowa 50311 (United States)
Publication Date:
OSTI Identifier:
21056919
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 901; Journal Issue: 1; Conference: ICAMDATA: 5. international conference on atomic and molecular data and their applications, Meudon (France), 15-19 Oct 2006; Other Information: DOI: 10.1063/1.2727362; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ARGON; ATOMS; COUPLING; CROSS SECTIONS; ELECTRON-ATOM COLLISIONS; ELECTRON-ION COLLISIONS; ELECTRONS; HELIUM; IRON IONS; NEON; PHOTOIONIZATION; PHOTON-ATOM COLLISIONS; PHOTON-ION COLLISIONS; R MATRIX; SCATTERING; WAVE FUNCTIONS; XENON; ZINC

Citation Formats

Bartschat, Klaus, and Zatsarinny, Oleg. High-Precision Cross Sections for Low-Energy Electron-Atom Collisions. United States: N. p., 2007. Web. doi:10.1063/1.2727362.
Bartschat, Klaus, & Zatsarinny, Oleg. High-Precision Cross Sections for Low-Energy Electron-Atom Collisions. United States. doi:10.1063/1.2727362.
Bartschat, Klaus, and Zatsarinny, Oleg. Fri . "High-Precision Cross Sections for Low-Energy Electron-Atom Collisions". United States. doi:10.1063/1.2727362.
@article{osti_21056919,
title = {High-Precision Cross Sections for Low-Energy Electron-Atom Collisions},
author = {Bartschat, Klaus and Zatsarinny, Oleg},
abstractNote = {We describe a recently developed B-spline R-matrix method for electron and photon collisions with atoms and ions. Using non-orthogonal sets of orbitals to construct the target description and to represent the scattering functions, this implementation of the close-coupling approach allows us to employ highly correlated target wavefunctions with relatively small configuration expansions. Example results from recent applications of the method for accurate calculations of low-energy electron scattering from He, Zn, Ne, Ar, Xe, and Fe+ are presented.},
doi = {10.1063/1.2727362},
journal = {AIP Conference Proceedings},
number = 1,
volume = 901,
place = {United States},
year = {Fri Apr 06 00:00:00 EDT 2007},
month = {Fri Apr 06 00:00:00 EDT 2007}
}
  • Various high-energy calculations of proton-multielectron-atom differential capture cross sections are compared with each other (and with the data on p+Ar K-shell capture). The proton-core interaction, including screening from the core electrons, is found to affect significantly the differential cross sections. I speculate that final-state interactions of the hydrogen atom with the target electrons of large atomic targets play a significant role in capture events and are in part responsible for the poor agreement with the Ar data. (AIP)
  • An experimental apparatus is described for measuring the total absolute cross sections for the production of free electrons in collisions of ions with gas atoms at energies down to threshold. The apparatus makes use of the fact that a homogeneous rf field in the collision chamber causes essentially no changes in the trajectories of the ions of the primary beam but does deflect electrons formed in the collision region from the point at which they are formed. A secondary-electron multiplier operating in the counting mode is used to detect the electrons and, thus, to increase the sensitivity of the method.more » The calculated and experimental energy spectra of the electrons formed in the collision chamber reveal well-localized groups corresponding to the appearance of electrons from the surfaces and from the target gas. Accordingly, when a two-level retarding system is used to isolate the group of electrons corresponding to ionization of the gas it is possible to avoid the distortion of the function dependence of the ionization cross section on the collision energy which would result from the secondary-emission electrons from the surfaces. The errors of the method are discussed. The collision chamber and the electron detector are designed so that the electrons formed in the ionization of the gas atoms can be corrected efficiently (efficiency approx.48%) under the particular working conditions (field frequency f=50 MHz) and peak value V/sub 0/=200 V). With this experimental apparatus it is possible to measure the absolute values of the total ionization cross section and to study the behavior of these cross sections down to threshold.« less
  • Previous calculations of ion-atom interactions by the pseudopotential and asymptotic methods are used in the computation of the cross section for symmetric charge transfer at energies below 1 keV. The results for Li/sup +/, Na/sup +/, K/sup +/, Rb/sup +/, Cs/sup +/, and Ca/sup +/ ions are compared with data obtained in beam experiments, and by optical-pumping techniques. The difference in the cross sections for /sup 2/P/sub 1///sub 2/ and /sup 2/P/sub 3///sub 2/ ions of Kr/sup +/ and Xe/sup +/ at thermal energies is studied, and the predictions are compared with recent mobility measurements. Cross sections are obtained formore » U/sup +/-U collisions, and the dependence of the thermal cross section on the polarizability is described. Symmetric charge transfer of the negative ions H/sup -/, Na/sup -/, and Cs/sup -/ is discussed briefly. (AIP)« less
  • The collision cross sections of sodium from the ground state to the first four excited states at the incident energy ranging from 0 to 5.4 eV are calculated using the R-matrix method. The convergences of the cross sections are checked systematically by using four sets of high-quality target states, i.e., 5, 9, 14, and 19 physical target states. The influence of the Rydberg target states on the collision cross sections is also elucidated at higher incident energies; i.e., the amplitude of resonance structures will decrease with respect to the effective quantum number {upsilon} of the Rydberg target states. This resultmore » is very useful for the calculations of these cross sections at intermediate energy with finite target states by combining the partial-wave-expansion methods valid at low energy with the first Born approximation method valid at high energy, which would be of great importance in obtaining complete cross-section data for related scientific fields.« less