(E,2E) IN THE VICINITY OF AN AUTOIONIZING STATE AS A PERFECT EXPERIMENT TO MEASURE PARAMETERS OF THE ELECTRON-IMPACT IONIZATION PROCESS

We consider the possibility of treating (e, 2e) experiments in the reg ion of autoionizing resonances as 'perfect experiments' in which param eters relating to the direct and resonance ionization amplitudes can b e determined. An angle-independent parameter is defined for the autoio nization of a doubly excited s-state to the s-state of an ion. Experim ental values of this parameter from recent data for decay of the (2s(2 ))S-I state of helium to the (1s)S-2 state of the helium ion are discu ssed. The more general situation involving states with L > 0 is outlin ed.