DOUBLE-IONIZATION OF HELIUM BY FAST ELECTRONS - THEORETICAL INVESTIGATIONS OF THE FOURFOLD DIFFERENTIAL CROSS-SECTION

Recent electron-impact double ionization (e, 3 - 1e) experiments on he lium are investigated theoretically. An ab initio calculation has been performed on the basis of the first Born approximation using differen t correlated wavefunctions for the initial bound-state and a correlate d double-continuum wavefunction which satisfies the exact asymptotic b oundary conditions for the final state with two slow electrons. The re sults of this calculation are compared with those of other theories.