State-selective differential cross sections for single and double electron capture inHe+,2+-Heandp-Hecollisions

Using the cold target recoil ion momentum spectroscopy technique, we have measured state-selective projectile scattering angles for single and double electron captures in collisions of protons and ${\text{He}}^{1,2+}$ projectiles with a helium target for incident energies of 60–630 keV/u. We also report theoretical results obtained by means of four-body one-channel distorted-wave models (continuum distorted-wave Born final state, continuum distorted-wave Born initial state, and Born distorted wave) and find mixed agreement with the measured data.