Production of energetic positronium at metal surfaces

Abstract

The production of positronium with kinetic energy greater than the positronium negative work function is clearly shown by time-of-flight spectroscopy of annihilating triplet positronium produced by the bombardment of low-energy positrons on metals. This higher-energy positronium channel is believed to be a consequence of positrons inelastically backscattered through the metal surface. At positron bombarding energies less than 100 eV, the positronium produced from backscattered positrons can be more intense than that produced by the diffusion of thermalized positrons to the surface.