Observation of Electron Capture into Continuum States of Neutral Atoms

Energy spectra of electrons ejected in the forward direction from 75-keV/amu He⁰-He,Ar collisions have been measured in coincidence with the charge-state-selected outgoing projectiles He⁰, He⁺, and He²⁺. The appearance of the cusp-shaped peak in the electron spectrum in coincidence with He⁰ gives the first clear experimental evidence that electron capture into the continuum states (ECC) occurs in collisions where the projectile is a neutral atom. The ECC for He⁰ impact is characterized by a considerably smaller width of the cusp peak than for He⁺ impact.