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Three-photon annihilation of ortho-positronium in argon gas

Journal Article · · Can. J. Phys., v. 51, no. 5, pp. 537-548
DOI:https://doi.org/10.1139/p73-070· OSTI ID:4334299
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Marked deviations from simple exponential decay are known to characterize the two-photon annihilation of positrons in the noble gases. In this experiment, a quadruple coincidence system was used to examine the detailed shape of three-photon positron lifetime spectra in argon. No deviation from a simple exponential was observed over the density range 2.57 to 33 amagat, except when a high electric field was applied. The ability to distinguish threephoton ortho-positronium annihilation from other modes of positron annihilation permitted, for the first time, a detailed investigation of the density dependence of the annihilation of ortho-positronium in a simple monatomic gas. Over the whole density range, the ortho-positronium annihilation rate was found to depend linearly on density, with a value of 7.15 plus or minus 0.10 mu s/sup -1/ for the vacuum rate of ortho-positronium annihilation and 0.250 plus or minus / 0.015 mu s/sup -1/ amagat/sup 1/ for the quenching rate of positronium in argon. With a field of 125 V cm/sup -1/ amagat/sup -1/ (at 2.57 amagat), a deviation from simple exponential decay was observed, a deviation whose shape is shown to be consistent with an interpretation in terms of time-delayed enhanced positronium production from the equilibrium free positron population. (auth)
Research Organization:
Univ. of British Columbia, Vancouver
NSA Number:
NSA-29-016798
OSTI ID:
4334299
Journal Information:
Can. J. Phys., v. 51, no. 5, pp. 537-548, Journal Name: Can. J. Phys., v. 51, no. 5, pp. 537-548; ISSN CJPHA
Country of Publication:
Canada
Language:
English

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Related Subjects

*POSITRONIUM-- ANNIHILATION
*POSITRONS-- ANNIHILATION
ARGON
EMISSION
GASES
LIFETIME
N60300* --Physics (Atomic & Molecular)--Positronium
Muonium
& Mesic Atoms & Molecules
PHOTONS
SPECTRA
TIME DEPENDENCE