Stueckelberg angular scattering oscillations in two-electron capture by C4+from He at low energies

Two different experiments have observed oscillations in the angular scattering intensity for the ground-state double-capture reaction C 4+ +He to C 2+ +He 2+ +Q at laboratory impact energies ranging from 300 eV to 1.5 keV. They were first observed as oscillations in the low-energy tail of energy gain distributions and were later verified in a direct angular differential cross section measurement. A two-state curve-crossing model is used to explain the oscillations as Stueckelberg oscillations deriving from an interference between two different reaction paths leading to the same scattering angle.