Total cross section for the dissociative excitation of He-2(+) molecular ions in collision with He

Abstract

Absolute cross sections have been determined for the dissociative excitation and electron capture followed by ion-pair formation (He++He-) for He-2(+) collisions with He in the energy range of 4-10 keV. The He+ absolute cross section that is uniquely due to the dissociative excitation was deduced, taking advantage of the measurements of the He- cross section. The center-of-mass energy for the fragment ions was measured. The available potential-energy curves show that the vibrationally excited ground state may be responsible for the fragment ions. The collisional deactivation of He-2(+) ions using high source pressure showed no effect on the measured cross section. Complete theoretical high-lying repulsive potential-energy curves for He-2(+) ions are currently not available, therefore it is not possible to quantitatively establish the final state of the ions.