Experimental support for physisorbed positronium at the surface of quartz
- 1 November 1985
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review B
- Vol. 32 (9) , 6067-6070
- https://doi.org/10.1103/physrevb.32.6067
Abstract
We report temperature-dependent positronium (Ps) emission from a single crystal of using a monoenergetic positron beam. Slow positrons () from an electrostatic beam system were injected with variable energy (0–1600 eV) into the target and Ps emission from the target surface was studied as a function of incident energy (E) as well as target temperature (T). Our data suggest a physisorbed Ps surface state which is temperature activated into a ‘‘slow’’ Ps emission with an activation energy of ∼0.15 eV. In addition, a large Ps yield (40% of the incident positrons are emitted as Ps at 400 eV) is observed even for T→0, attributed to ‘‘fast’’ Ps produced by the bulk Ps formed within the target and diffusing to the surface. From the Ps yield vs E we find a bulk Ps diffusion constant of 0.047±0.013 /sec. We also observe a slow reemission yield of (15±2)% at 400-eV incident energy.
Keywords
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