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

Journal Article · Thu Dec 15 04:00:00 EST 2005 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.72.0· OSTI ID:20786301

Marler, J P; Surko, C M ^[1]

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1. Department of Physics, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0319 (United States)

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.

• OSTI ID: 20786301
• Journal Information: Physical Review. A, Journal Name: Physical Review. A Journal Issue: 6 Vol. 72; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

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