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Title: Systematic comparison of positron- and electron-impact excitation of the {nu}{sub 3} vibrational mode of CF{sub 4}

Abstract

Absolute measurements are presented for the excitation of the {nu}{sub 3} vibrational mode in CF{sub 4} by positron and electron impact from 0.1 to 2 eV. To minimize systematic differences, these measurements were made using the same trap-based electron or positron beam, associated experimental apparatus, and procedures. Unlike other vibrational excitation cross sections studied to date, the near-threshold cross section for the {nu}{sub 3} vibrational mode in CF{sub 4} is similar, both in magnitude and shape, for positrons and electrons. Comparison of the cross sections with an analytic Born dipole model yields good agreement, while comparison of this model with other measured positron-impact vibrational cross sections indicates that the contribution of this long-range dipole coupling varies widely. The maximum value of the cross section in CF{sub 4} is the largest of any positron-impact vibrational excitation cross section measured to date. This provides a likely explanation of the observation that CF{sub 4} is very effective when used as a buffer gas to cool positron gases and plasmas.

Authors:
;  [1]
  1. Department of Physics, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0319 (United States)
Publication Date:
OSTI Identifier:
20786301
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 72; Journal Issue: 6; Other Information: DOI: 10.1103/PhysRevA.72.062702; (c) 2005 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; CARBON TETRAFLUORIDE; COMPARATIVE EVALUATIONS; COUPLING; CROSS SECTIONS; DIPOLES; ELECTRON-MOLECULE COLLISIONS; ELECTRONS; ENERGY TRANSFER; EV RANGE; EXCITATION; PLASMA; POSITRON BEAMS; POSITRON-MOLECULE COLLISIONS; POSITRONS; TRAPS

Citation Formats

Marler, J. P., and Surko, C. M. Systematic comparison of positron- and electron-impact excitation of the {nu}{sub 3} vibrational mode of CF{sub 4}. United States: N. p., 2005. Web. doi:10.1103/PHYSREVA.72.0.
Marler, J. P., & Surko, C. M. Systematic comparison of positron- and electron-impact excitation of the {nu}{sub 3} vibrational mode of CF{sub 4}. United States. doi:10.1103/PHYSREVA.72.0.
Marler, J. P., and Surko, C. M. Thu . "Systematic comparison of positron- and electron-impact excitation of the {nu}{sub 3} vibrational mode of CF{sub 4}". United States. doi:10.1103/PHYSREVA.72.0.
@article{osti_20786301,
title = {Systematic comparison of positron- and electron-impact excitation of the {nu}{sub 3} vibrational mode of CF{sub 4}},
author = {Marler, J. P. and Surko, C. M.},
abstractNote = {Absolute measurements are presented for the excitation of the {nu}{sub 3} vibrational mode in CF{sub 4} by positron and electron impact from 0.1 to 2 eV. To minimize systematic differences, these measurements were made using the same trap-based electron or positron beam, associated experimental apparatus, and procedures. Unlike other vibrational excitation cross sections studied to date, the near-threshold cross section for the {nu}{sub 3} vibrational mode in CF{sub 4} is similar, both in magnitude and shape, for positrons and electrons. Comparison of the cross sections with an analytic Born dipole model yields good agreement, while comparison of this model with other measured positron-impact vibrational cross sections indicates that the contribution of this long-range dipole coupling varies widely. The maximum value of the cross section in CF{sub 4} is the largest of any positron-impact vibrational excitation cross section measured to date. This provides a likely explanation of the observation that CF{sub 4} is very effective when used as a buffer gas to cool positron gases and plasmas.},
doi = {10.1103/PHYSREVA.72.0},
journal = {Physical Review. A},
number = 6,
volume = 72,
place = {United States},
year = {Thu Dec 15 00:00:00 EST 2005},
month = {Thu Dec 15 00:00:00 EST 2005}
}