Transfer excitation in He++He collisions studied by 0 degrees electron spectroscopy

Abstract

Spectra of autoionisation electrons from helium projectiles have been measured in collisions of 50-500 keV 3He+ ions with He target atoms. Kinematic line broadenings were substantially reduced by observing electrons at 0 degrees with respect to the incident beam. Lines attributed to states such as 2s2 1S, 2s2p 3P,2p2 1D and 2s2p 1P were resolved. The 2s2p 3P state was found to be predominantly produced exhibiting an asymmetric lineshape (Fano profile) that arises from an interference between transfer excitation and electron capture to the continuum (ECC). Absolute transfer excitation cross sections were deduced from the data. The cross section for the production of the 2p2 1D state exhibits a maximum at about 350 keV projectile energy showing that electron-electron interaction may play an important role in the excitation process.