Electron correlation plays a central role in any system involving Coulomb interactions and the recent advances in coincidence experiments have brought into focus its role in continuum and bound states. Electron correlation has been the subject of several recent investigations using both electrons and photons as a probe. In particular, single and double ionisation coincidence experiments are reviewed with emphasis on inner shell processes.
Stefani, G., Avaldi, L., Camilloni, R. (1994). CORRELATION IN INNER-SHELL IONIZATION STUDIED BY COINCIDENCE EXPERIMENTS RID G-7348-2011. NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH. SECTION B, BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 87(1-4), 253-258 [10.1016/0168-583X(94)95269-8].