Positronium Formation on the Rhenium Surface Studied by Slow Positron Measurements

The article reports measurement results performed using slow positron beam techniques in pure well‐annealed rhenium samples at a depth of less than 0.5 μm from the entrance surface. The Doppler broadening of the annihilation line and positron lifetime results are presented. The minimal value of the positron diffusion length is found to be about 4.10 ± 0.12 nm. The positron lifetime at the surface is about 350–400 ps; however, the bound state, that is, positronium, is detected as well. This state is not observed in the samples exposed to cold rolling. It also presents calculations of the positron diffusion model, including the formation of positronium at the entrance surface.