Abstract.The production of H + ions resulting from single collisions of mass-selected ionic hydrogen clusters, tt + (n = 9, 25, 31), with helium at high velocity (1.55 times the Bohr velocity) has been studied. A strong double H3 ~ ion production resulting from one incident cluster is observed. Moreover, evidence for a triple H I fragment production is presented for n = 25 and 31. Thus, in this energy range, the collision gives rise to multifragmentation processes. The formation of H~ ions takes place in the fragmentation of the multicharged cluster resulting from the collision. Since this observation, H + infrared emission has been detected in many astronomical objects. Because of a great reactivity and its large amount in nature, H + is assumed to play a central role in the chemical evolution of interstellar molecular clouds [8]. This H + abundance is usually explained by the efficient exothermic reaction
+ + H2-+ + H.In this paper, we report on the first experimental observation of multiple H + production after fragmentation of mass-selected 60-keV/amu ionic hydrogen clusters, H + (n=9, 25, 31), induced by single collision with helium.