Differential Experimental Investigation of Electron Capture for He2+ on Helium at Low Energy

State-selective single- and double-electron capture in He(2+)-He collisions at energies ranging from 20 to 40 keV have been studied experimentally by means of cold target recoil ion momentum spectroscopy. The differential cross sections have been obtained by measuring the longitudinal and transverse momenta of recoil ions. The results show that single electron capture into L shell is the dominant reaction channel, and double-electron capture into the ground state of projectile is by far the dominant process in the incident energy range. The measured state-selective cross sections agree well with the semi-classical close-coupling calculations.