Eur. Phys. J. D (2015) 69: 34
https://doi.org/10.1140/epjd/e2014-50635-y

Regular Article

Experimental (e,2e) study of state-to-state interference between autoionizing states of He^*

Institute of Physics, University of Miskolc, 3515 Miskolc-Egyetemváros, Hungary

^a e-mail: fizpari@uni-miskolc.hu

Received: 28 August 2014
Received in final form: 11 November 2014
Published online: 3 February 2015

Abstract

The electron impact excitation of the autoionizing states of helium, their subsequent decay into the same He⁺1s^-1 final ionic state, and the interference of these processes are studied. The scattered-ejected electron pairs are observed in coincidence by two electron spectrometers. A constant ionic state (e,2e) experiment (CIS) is performed, isolating the final state by keeping the sum of transmission energies of the spectrometers constant. The focus of this work is on the exchange interference effects of the 2s²(¹S) and 2p²(¹D) autoionizing states of helium. Around the critical energy (where the energy of the scattered electron from one reaction channel equals the energy of the ejected electron released along the other reaction channel), even a few tenths of eV modification in primary energy causes a significant change in the CIS spectra, which indicates the presence of exchange interference effects.