An experimental study of autoionization processes occurring in 2 eV-1 keV He2+-Hg collisions

An apparatus developed for the investigation of low-energy ionizing collisions between multiply charged ions and other particles by electron and ion spectroscopy is described, and results of a detailed study of the He2+/Hg system in the collision energy range from 2 eV to 1 keV are reported. In this energy range the ionization leads to formation of He+ and Hg2+ in its ground state and four lowest excited states arising from the 5d96s configuration. The ionization cross section has a maximum at about 25 eV and drops by about an order of magnitude between the maximum and 2 eV, and also between the maximum and 400 eV. An analysis of the electron and ion energy spectra leads to the conclusion that the ionization mechanism is molecular: at large separations the system undergoes charge exchange, and at separation of about 5a0 the system autoionizes from the three potential curves. A potential curve model is proposed. (author)