Ejected-electron energy spectra in low energy positron-argon collisions

Energy spectra of electrons ejected from an argon target by positron impact have been measured and compared with theoretical expectations. No major cusp structure was observed in any of these spectra. Instead a small ridge is present in some cases at energies compatible with electron capture to continuum (ECC) states of positronium. Its magnitude suggests that ECC makes a minor contribution to ionization by a light positively charged projectile. (Author)