STUDIES OF AUTOIONIZATION WITH (E,2E) SPECTROSCOPY

Recent advances in the study of double excitation-autoionization proce sses in helium using the (e,2e) technique are reviewed. Experiments at Flinders (Australia) and Newcastle (UK) provide the first reliable ex perimental data and have provoked the development of new theoretical a pproaches to the problem. Comparisons with recent calculations of the coincident electron spectra and parameters characterising the resonanc e states are presented for different kinematic conditions. Since the r esonance parameters contain complex amplitudes relating to the resonan ce excitation, and direct and resonance ionization, they are extremely sensitive to the dynamics of the reaction and the atomic structure. H ence they provide the most rigorous test of the theory of ionization b y electron impact.