Investigation of positronium formation at a Ag(100) surface

Positronium formation as a function of sample temperature and incident energy was studied on a Ag(100) surface with monoenergetic positrons. A constant re-emission of positronium from the Ag sample at room temperature is associated with special sites, presumably defects or impurities on the surface. An increase in the positronium fraction as a function of temperature is identified as detrapping from a surface trap. (author)