Single- and double-electron detachment in collisions of two negative hydrogen ions

Abstract

Employing the crossed-beams technique in conjunction with a beam-pulsing method, we have measured absolute cross sections sigma tot for the process H-+H- to H0+... for CM energies between 2.5 and 100 keV. Combining the present results with our previously measured cross sections for double-electron detachment ( sigma 00) and triple-electron detachment ( sigma 0+). We obtain cross sections sigma 0- for the single-electron detachment process from the relation sigma 0-= sigma tot- sigma 00- sigma 0+ The experimental data of singleand double-electron detachment are well described by theoretical results based on the non-stationary tunnelling approach. Both cross sections are calculated for CM energies between 0.15 and 300 keV. A new two-electron simultaneous transition mechanism is introduced. The importance of this process for the theoretical assessment of the experimental results is discussed.