Elastic and Inelastic Scattering of Low-Velocity He+ Ions in Helium

Cross sections have been measured for both elastic and inelastic collisions of He+ ions in the energy range from 4 to 400 ev with helium atoms in the gas phase. Charge exchange was the only inelastic process observed except at the highest energies, where very small cross sections for ionization were obtained. Cross sections for charge exchange decreased slowly with increasing ion energy. The potential functions determined from the elastic scattering data are V=−34.5r−6.88 for r>1.7Aand V=−5.15r−2.90 for r<1.7A.Assuming an equilibrium distance of 1.1A the interaction energy for the formation of the molecular ion He2+ is calculated to be 3.9 ev.