High-energy electron impact study on autoionizing region in helium by detection of ejected electrons

Abstract

Ejected electron spectra from autoionizing region of He in the energy region of N=2 and N=3 Rydberg series have been measured at electron impact energies of 505, 1816 and 2018eV and ejection angles of 40°, 90° and 130°. At high electron impact energies and large ejection angles this energy region is dominated by optically allowed transitions, while optically forbidden transitions are less pronounced. At the angle of 40° optically forbidden states almost vanish and resonances dominate the spectrum. A new resonance at 64.18eV has been found at the angle of 40° and the electron impact energy of 505eV. In energy region above 65eV of excitation energy the first three levels of N=3 and the first level of N=4, Rydberg series have been measured. A good agreement in energy positions between these features and the corresponding ones reported by Domke et al.[2] was found.