Existence of free and self-trapped positronium states in alkali halide crystals: Theoretical analysis and comparison with experiment

I. V. Bondarev
Phys. Rev. B 58, 12011 – Published 1 November 1998
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Abstract

A variational calculation is performed of the eigenstates of a positronium atom coupled with a field of longitudinal acoustic phonons in ionic crystals at finite temperatures. On the basis of this calculation a theoretical analysis is made of the possibility of self-localization (self-trapping) of positronium. The self-trapped states of positronium in NaF, NaCl, KCl, and KI crystals are found to be metastable with the energy higher by 0.010.1eV with respect to the stable delocalized (free) states. The self-trapped states of positronium in MgF2 and αSiO2 crystals are unstable at absolute zero temperature and become metastable with an increase in temperature for T>300K. The difference in the energies of such “high-temperature” self-trapped states and the free states of positronium in MgF2 and αSiO2 is found to be at least one order of magnitude larger than that in the other alkali halides, explaining theoretically experimental evidence for the nonexistence of self-trapped positronium in these crystals. The basic characteristics (energy, effective mass, mean number of surrounding phonons, and localization radius) of the self-trapped and free states as well as the deformation potential constants are calculated for positronium in the crystals above. The results obtained are in good agreement with known experimental data.

  • Received 17 March 1998

DOI:https://doi.org/10.1103/PhysRevB.58.12011

©1998 American Physical Society

Authors & Affiliations

I. V. Bondarev

  • The Institute of Nuclear Problems, The Belarusian State University, Bobruiskaya Street 11, 220050 Minsk, Republic of Belarus

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Issue

Vol. 58, Iss. 18 — 1 November 1998

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