Simultaneous Ionization and Excitation of Molecules by Positron Impact

Cross sections for ionization excitation of molecules by positron impact have been measured for the first time by scattering a positron beam from CO₂ and N₂. The cross sections have been observed to exceed those for electron impact by up to a factor of ~3 for CO₂ and ~5 for N₂. The enhancement arises primarily via positronium formation. The cross sections account for up to ~12% and 20% of the total cross sections for positron scattering from N₂ and CO₂, respectively.