Formation of He+ ions in various electron states in He+2+He collisions

One-electron capture (He+2+He→He++He+) and electron capture with ionization (He+2+He→He++He+2+e-) due to He+2+He collisions are studied for He+2 kinetic energies T0=2-60 keV. The processes were recognized by recording both particles involved in a given collision act by the coincidence technique. For the first time the kinetic energy losses of the fast particle and its scattering angle are measured simultaneously with an analysis of the charge states of the particles. As a result it is possible to measure the cross section for the elementary processes of charge state change with the formation of particles in definite electron states and for a given impact parameter. It is shown that with an overwhelming probability (approximately 75% for T0=60 keV and approximately 100% for T=2 keV) one of the He+ ions produced in the capture process is in the excited state. The energy spectra of the electrons removed in the capture with ionization process are determined which correspond to a fixed value of the impact parameter. The dependence of the spectra on the impact parameter shows that the ionization with capture process is the result of decay of the self-ionization state of the He22+ quasimolecule. The internuclear distances (determined from the scattering of the He+ ions) at which inelastic transitions occur agree with those expected on basis of the He22+ term system. It is concluded that He+2+He collisions can satisfactorily be described by the quasimolecular model of interaction of atomic particles