Coincidence Studies of Electron and Photon Impact Ionization

The great advantage of coincidence measurements is that by suitable choice of the kinematical and geometrical arrangement one may probe delicate physical effects which would be swamped in less differential experiments. The measurement of the triple dif ferential and higher-order cross sections presents enormous technical difficulties, but refined experiments of this type provide an insight into the subtleties of the scattering process and offer a welcome, if severe, test of the available theoretical models. The last few years have been an exciting time to work in the field and much has been learned. Profound insights have been gleaned into the basic Coulomb few body problem in atomic physics: the experimental study of the fundamental (e,2e) processes on hydrogen and helium targets continues to add to our knowledge and indeed to challenge the best of our theoretical models; significant advances have been made in the understanding of the "double excitation problem," that is the study of ionization processes with two active target electrons: important measurements of (e,3e), (,),,2e), excitation-ionization and excitation autoionization have been reported and strides have been made in their theoretical description; the longstanding discrepancies between theory and experiment for relativistic (e,2e) processes were resolved, spin dependent effects predicted and ob served and the first successful coincidence experiments on surfaces and thin films were announced. Theory and experiment have advanced in close consort. The papers pre sented here cover the whole gambit of research in the field. Much has been achieved but much remains to be done.

Résumé
Proceedings of a European conference held in Belfast, Northern Ireland, September 5-7, 1996

Contenu
Recent Absolute (e,2e) Measurements on Atomic Hydrogen and Helium at Low and Intermediate Energies.- Second Born Calculations of (e-2e) Cross Sections at Low Energy Using a Pseudostate Set.- Excitation-Ionization and Excitation-Autoionization of Helium.- An Analytical Approach to Resonant and Direct Fragmentation of Many-Body Coulomb Systems.- Ionization Dynamics and Exchange Effects in Pure Three-Body Coulomb Scattering.- Analysis of Integrated Cross Sections and Spin Asymmetries for the Electron-Impact Ionization of One- and Two-Electron Atomic Systems.- Double Ionization Mechanisms from Triple Coincidence Experiments.- Double Ionization of Helium by Electron Impact: A Study of the Two-Step Mechanism.- Partitioning of Momentum in Electron-Impact Double Ionization.- 5DCS and 4DCS Calculations for Symmetric (e,3e) Impact Ionization.- Exact and Approximate Methods of the Rigorous Coulomb Scattering Theory.- Strong and Weak Statements in the Theory of Dipolar (e,2e) Impact Ionization.- The Triple Differential Cross Sections for (?,2e) in Helium at Intermediate Energies.- Total and Single Differential Cross Sections for He Double Photoionization Calculated by the CCC Method.- From (?,2e) to (?,eR): Kinematically Complete Experiments with COLTRIMS.- Angle Resolved Electron Energy Loss Study on the Inner Shell Excited States of Ne.- Circular Dichroism in Double-Photoionization of Helium Studied by Electron Time-of-Flight Coincidence Spectroscopy.- Interference Effects in Argon Auger Coincidence Spectra.- Triple Differential Cross Sections for Electron Impact Ionization of Argon between 50 eV and 215.8 eV.- Multiple Scattering Effects in High-Energy Electron Molecule Ionization of H2.- Parametrisation of TDCS in a Plane.- An Explanation of the Structure Observed inOut-of-Plane Symmetric Measurements on Helium.- On the Addition Theorem for Jacobi Polynomials.- Progress Report on Relativistic (e,2e) Processes.- Structure of the Triply Differential Cross Section in the Recoil Region in Relativistic Electron Impact Ionization.- Coulomb Boundary Conditions for Relativistic (e,2e) Processes.- Spin Effects in the (e,2e) Cross Sections of Xenon.- Measurements of Spin Polarized (e,2e) Processes at 54.4 eV.- Is There Any New Physics in Spin Dependent (e,2e) Collisions?.- Electron-Momentum Spectroscopy of Solids by the (e,2e) Reaction.- Valence Band Reconstruction in Graphite by Grazing Incidence (e,2e) Spectroscopy.- Energy Distribution of Correlated Electron Pairs Excited by Low Energy Electrons from W(001) Measured by a Time-of-Flight (e,2e) Spectrometer.- Electron Impact Ionization of Hydrogenic Ions in Asymmetric Geometries.- Bethe-Ridge Effects in (e,2e) on H? (Using 6DIME).- The Ehrhardt Prizes 1996.- Three-Body Models of Electron-Hydrogen Ionization.- The Normalisation of the Experimental Triple Differential Cross Section of Noble Gas Atoms in Extreme Asymmetric Geometry.