THE (E,2E) SPECTROSCOPY, ACHIEVEMENTS AND PERSPECTIVES

Electron-electron coincidence experiments have experienced over the pa st twenty years an increasingly rapid expansion and application to man y different fields. Among them, the (e,2e) spectroscopy has been succe ssfully used to investigate either the target electronic structure or the ionisation dynamics. The capability of this spectroscopy to invest igate single particle properties in atoms, molecules and solids is dis cussed by the help of some recent results. Correlation effects in boun d states and in the continuum have been the subject for several recent (e,2e) investigations. Single and double ionisation coincidence exper iments are reviewed focusing the attention on correlation effects. The interference between direct and resonant ionisation channels has been also the objective of recent electron coincidence experiments. Perspe ctive and developments of the (e,2e) spectroscopy are briefly discusse d.