On the shape of the (2s2)1S resonance in the spectra of electrons ejected from He atoms during their encounters with fast electrons and protons

Some aspects of the theoretical description of the intensity and shape of resonances observed in the spectra of electrons ejected from atoms by fast electrons and protons are discussed. Numerical calculations have been performed for the (2s 2 ) 1 S resonance of helium atoms. Dependences of the resonance intensity and shape on the collision kinematics, i.e. incident-particle energy and electron ejection angle, have been obtained. The considerable variations revealed in the character of the resonance asymmetry with varying ejection angle are associated with a strong interference between separate components of the transition amplitude.