Positron Dynamics in Rare-Gas Solids

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Abstract
Using a beam of slow positrons in ultrahigh vacuum, we estimate the positron mean free path and energy-loss rate and measure the inelastic thresholds due to exciton, electron-hole pair, and positronium formation in solid rare-gas targets. The measurements are used to explain the large emission energies of positrons from the wide-band-gap solids in terms of a hot-positron model. The large diffusion length of the hot positrons in the solid rare gases makes them very efficient moderators for producing slow positrons.