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Journal of Physics B Atomic and Molecular Physics

Excitation and delayed annihilation of Ps in a laser field

Farhad H. M. Faisal, P. S. Ray

Published Nov 14, 1981• 12 citations
Publisher

Abstract

Resonant excitation of Ps to the higher P states is found to influence strongly the probability of gamma emission by annihilation. A considerable population can be, at the same time, transferred to the upper states. Numerical results for the excitation of the 2 1 P and 2 3 P states and the annihilation of the 1 1 S and 1 3 S states are presented for a number of field strengths of interest.

DOI
10.1088/0022-3700/14/21/014

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Resonant excitation of Ps to the higher P states is found to influence strongly the probability of gamma emission by annihilation. A considerable population can be, at the same time, transferred to the upper states. Numerical results for the excitation of the 2 1 P and 2 3 P states and the annihilation of the 1 1 S and 1 3 S states are presented for a number of field strengths of interest.
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The fluorescence decay rate of 2 P J 3 positronium (Ps) atoms [ Γ fl ] has been experimentally determined using a Stark-mixing technique. Ground-state Ps atoms were optically excited in an electric field to states containing both 2 P J 3 and 2 3 S 1 components. The relative state populations were controlled via an applied mixing electric field, and a larger, pulsed, electric field was used to induce rapid quenching of the system after a fixed time delay. The dependence of the quenching signal on the mixing field strength was used to determine the relative and populations of the mixed states, whose decay rates are determined by the intrinsic self-annihilation and fluorescence decay rates. The measurements were compared to a trajectory simulation and Stark-mixing model, using the fluorescence decay rate as a free parameter. By finding the best agreement between the data and simulations we obtain Γ fl = 299 ± 25 µ s − 1 , which is consistent with the mean theoretical value of 313.343 ± 0.003 µ s − 1 . Published by the American Physical Society 2024