Collisions of ionized hydrogen clusters with helium atoms: electron capture as a function of the cluster size
Résumé
Electron capture cross sections of hydrogen cluster ions Hn+ colliding with atomic helium have been measured in a large range of cluster size (5⩽n⩽35) for the same velocity (1.5v0, 60 keV/u). While the electron capture cross section decreases from the H+ ion to the H3+ one, the cluster electron capture cross section is found to be independent of the cluster size and nearly equal to the capture cross section of the H3+ ion. Electron capture by hydrogen clusters on a helium atom is a process involving only the H3+ core of the cluster where the positive charge is localized. It appears that this very localized electron capture is not disturbed by the presence of molecules, up to sixteen, around the H3+ core.