Abstract
A series of angular correlation spectra for positrons annihilating in the noble gases and in gas mixtures has been obtained using the University of East Anglia two-dimensional angular correlation spectrometer.l Beta positrons from a sodium-22 source are guided by a O.8T magnetic field to the interaction region, which is first evacuated and then filled with gas at 1 bar pressure at room temperature. Gamma cameras placed at 3m on either side of the sample chamber record the two-photon annihilations of free positrons and positronium (Ps) atoms in a 9mm-diameter volume of gas at the centre of the cell. Events recorded include annihilation from the triplet (m = O) — singlet state, which at O.8T is 91% mixed and has a mean lifetime of 9.7ns. In contrast, a negligible number of two-photon decays are rec — orded from (triplet) o-Ps atoms quenched on the (distant) walls of the gas cell or through collisions with gas atoms within the viewed volume.
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P.G. Coleman, T.C. Griffith, G.R. Heyland and T.L. Killeen J.Phys.B. 8, L185 (1975).
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© 1987 Plenum Press, New York
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Coleman, P.G., Rayner, S., West, R.N., Charlton, M., Jacobsen, F. (1987). Angular Correlation Studies of Positron and Positronium Annihilation in Gases. In: Humberston, J.W., Armour, E.A.G. (eds) Atomic Physics with Positrons. NATO ASI Series, vol 169. Springer, Boston, MA. https://doi.org/10.1007/978-1-4613-0963-5_36
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DOI: https://doi.org/10.1007/978-1-4613-0963-5_36
Publisher Name: Springer, Boston, MA
Print ISBN: 978-1-4612-8267-9
Online ISBN: 978-1-4613-0963-5
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