INVESTIGATION OF THE SPONTANEOUS IONIZATION MECHANISMS IN SLOW COLLISIONS OF HE+ WITH CA AND BA, AND OF NE+ WITH BA

In the collision energy range 2-1000 eV, the ionisation processes occurring in collisions of He+ with Ca, Ba, and Ne+ with Ba, are studied by electron spectroscopy. From the observed electron spectra, and from the variation with collision energy, details on the respective mechanisms are derived, and numerical data on the relevant potential curves obtained. It is found that in the He+/Ba system ionisation occurs as atomic autoionisation of Ba+* after the collision is completed, while the He+/Ca system autoionises at small separations during the collision. In Ne+/Ba both these mechanisms are observed. For the analysis of molecular autoionisation spectra new semiclassical formulae are derived and their validity shown by comparison to the He+/Ca spectra.