ATOMIC INNER-SHELL THRESHOLD EXCITATION PHENOMENA

Abstract
Photoionization of atomic inner shells in the threshold regime permits observation of the onset of multiple excitation processes and post-collision interaction. Some aspects of the interpretation of these phenomena in terms of atomic structure and dynamics are discussed. The study of threshold processes is among the most interesting and fruitful approaches to a deeper understanding of atomic and molecular structure and dynamics. This field has become accessible to detailed investigation through the advent of tunable, highly monochromatic synchrotron radiation. Rapid progress is being made, as demonstrated by a number of reports at this Conference. I want to touch on - two topics related to threshold phenomena that arise from Coulomb correlation : multiple photoexcitation and post-collision interaction.