Observation of an impact-parameter window in low-velocity ionizing collisions of Ne+ on Ne proceeding through quasimolecular states

Target ionization in collisions of singly charged Ne+ ions with Ne has been investigated at projectile velocities from 0.25 to 0.55 a.u. using electron and recoil momentum imaging techniques. The momentum distributions of the ejected electrons were found to carry a distinct signature strongly suggesting that ionization is taking place by successive promotions through molecular orbitals. The observed recoil transverse momentum distributions are donut-shaped, indicating that single ionization is confined to a well-defined impact-parameter window. [S1050-2947(98)50311-3].