Emission of Band-Gap-Energy Positrons from Surfaces of LiF, NaF, and Other Ionic Crystals
- 26 November 1984
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 53 (22), 2165-2168
- https://doi.org/10.1103/physrevlett.53.2165
Abstract
Energetic positrons implanted into various ionic crystal surfaces are reemitted with a maximum kinetic energy (14.7 ± 0.7 eV for LiF) near the band-gap energy. The evidence suggests that, at least for LiF and NaF, the emission originates from bulk-formed positronium (Ps) breaking up after diffusing to the surface. In our model, the positrons are Auger emitted when the Ps electrons recombine with holes at the surface, and the spectrum of positron energies thus reflects the density of empty surface states.Keywords
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