Positronium formation in molecular oxygen

J. Archer, S.M. Trilov, P.G. Coleman

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Abstract

New measurements of the positronium (Ps) formation cross section in molecular oxygen have been made using the 'positron loss' technique used in earlier measurements in the noble gases-the reduction in beam intensity being attributed to Ps formation. The results are generally in agreement, in terms of dependence on incident positron energy, with earlier measurements, but are lower in magnitude than those deduced from total ionization measurements below the first threshold for direct ionization, which employed ion detection. Q for molecular oxygen exhibits an interesting peak-like dependence on incident positron energy just above threshold, and possible reasons for this structure are discussed. These include the possibility of a dissociative attachment process; a unique peak at similar projectile energies has long been observed in electron-oxygen scattering. The most likely explanation, however, lies in coupling between Ps formation and excitation to the continuum, the latter having previously been shown also to have a peaked energy dependence above threshold.
Original languageEnglish
Article number012001
Number of pages4
JournalJournal of Physics: Conference Series
Volume443
Issue number1
Early online date10 Jun 2013
DOIs
Publication statusPublished - 2013
Event16th International Conference on Positron Annihilation - Bristol, UK United Kingdom
Duration: 19 Aug 201224 Aug 2012

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