Excitation mechanisms in He+-He collisions

Abstract

ABSTRACT Single-electron excitation of He atoms by 30 and 50 keV He+ impact was investigated using anticrossing spec-troscopy. The measured anticrossing spectra give evidence for the assumption that in the intermediate energyrange, where the excitation cross-sections have resonance-like maxima, excitation proceeds via Paul-trap pro-motion. The electron to be excited gains energy by transiently riding during the collision on the saddle of thetwo-center potential of the (He+)2 molecular core.Keywords: Stark effect, anticrossing spectroscopy. 1. INTRODUCTION The )rototype system for studying single-electron excitation in ion-atom collisions is H+_H, where only oneelectron is present. This symmetric collision system can he described semiclassically, that is it can be presumedthat the protons move on classical trajectories and only the motion of the electron must be treated quantum dynamically. The evolution of the state of the electron initially in the is groundstate of the hydrogen atom H depends on the velocity v and the impact parameter b of the hydrogen ion H+ colliding with the atom. If