H 2 + and H 3 + ions, produced in a H 2 plasma of a radio-frequency ion source, were accelerated to 6-60 keV and directed into a gas target of Krypton. The cross sections for the formation of H + and H - resp. H 2 + , H + and H - have been measured. In the case of H + , obtained from the dissociation of H 2 + , 2 maxima have been found in the present energy range. A third is known to be at about 100 keV. We discuss the applicability of the Massey' adiabatic hypothesis, known from the analysis of charge-exchange experiments, to the maxima in the cross-section vs. energy curve for dissociation experiments.