SINGLE-ELECTRON AND DOUBLE-ELECTRON DETACHMENT IN COLLISIONS OF 2 NEGATIVE HYDROGEN-IONS

Employing the crossed-beams technique in conjunction with a beam-pulsi ng method, we have measured absolute cross sections sigma(tot) for the process H- + H- --> H-0 +... for CM energies between 2.5 and 100 keV. Combining the present results with our previously measured cross sect ions for double-electron detachment (sigma(00) and triple-electron det achment (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 single- and double-e lectron detachment are well described by theoretical results based on the non-stationary tunnelling approach. Both cross sections are calcul ated for CM energies between 0.15 and 300 keV. A new two-electron simu ltaneous transition mechanism is introduced. The importance of this pr ocess for the theoretical assessment of the experimental results is di scussed.