Cross sections for single and double electron capture from He++ on hydrogen, neon and argon.

Abstract

Cross sections σ21 and σ20 from doubly charged helium ions have been measured in H 2, Ne and Ar. The measurements were performed in the velocity range 1.6-4.4 x 10 7 cm /s. 3He++ was used as a projectile as 4He++ could not be separated from background H2 by magnetic deflection in our apparatus. Isotope effects are known to be negligible in this velocity range. Results obtained for the double electron-capture process at low energies indicate near resonant ( Ae ~ 0 ) types of collisions which show that in the case of processes He++ + X —>He + X++ where X is Ne or A r, the recoiling doubly-charged ions are produced in highly-excited states. Structure is observed in the cross sections versus velocity curves for collisions with Ne targets