Phenomena associated with near-threshold excitation of autoionizing levels of helium by electron impact

It is shown that the post-collision interaction model, previously proposed to explain the energy shifts of electrons ejected from autoionizing states of He excited by low-energy charged particles, can be extended to include cases where very low-energy scattered electrons are recaptured to form singly excited bound states. Electron excitation functions of three band states of He are presented over the range 57 to 60 eV. The photon yield from He over the incident energy range 56 to 61 eV is interpreted in the light of the above findings.