Transfer Ionization in He-2+-h- Collisions - Measurement of the Exothermicity and Theoretical Interpretation

The energy imparted to the ions in the transfer ionization reaction He2+ + H- --> He+ + H+ + e has been measured in a merged beam experiment using two different techniques (magnetic analysis and time of flight). The result obtained in both cases is of the order of 6 eV and confirms that the transfer ionization proceeds in two steps: a single electron transfer at large internuclear separation followed by a resonant Penning ionization at small distances. With this view, a simple calculation of the cross section is presented, with results that are in good agreement with the available experimental data.