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An (e,2e) experiment is the measurement of an electron impact ionization process where both the exiting electrons are detected in coincidence. Such measurements are almost at the limit of what can be known, in quantum mechanical terms, and its description presents a substantial theoretical challenge. There are at least two very good reasons for studying (e,2e) and related processes. In the first place we are now only beginning to understand the dynamics of the collision process. The range and sophistication of present experiments allow us to identify kinematic regimes where delicate and subtle effects can be observed, stretching current theories to their limit. Secondly, the multiple coincident technique offers us the possibility of an analytical tool that could be used to probe the structure of the target, be it atom, molecule, thin film or surface. Measurements are now being performed at threshold on H, on the inner shell levels of Au and Ag using projectiles at relativistic energies, with spin-polarized electrons on Li, on a myriad of molecules in symmetric, noncoplanar kinematics, and on He in a multitude of different geometries. The technique has recently been extended to excitation ionization (e,3e) and (gamma,2e) experiments. Major theoretical advances have also been made, but much still remains to be done.
This volume contains the invited papers that were presented at the Workshop on (e,2e) and related processes which took place in September/October 1992 in Cambridge, UK. The three major review papers which it contains together form an excellent introduction to this new and rapidly expanding area of physics and set the scene for the wide range of research contributions, both experimental and theoretical, from the leading scientists in the field.
Table des matières
(e,2e), effective charges, distorted waves and all that.- Directions in (e,2e) and related processes.- Near theshold (e,2e) ionisation of helium and atomic hydrogen.- Does asymmetric (e,2e) approach the dipolar limit at intermediate energies.- Knockout reactions to study atomic and molecular electronic structure: the future.- Absolute experimental cross sections for symmetric coplanar (e,2e) collisions of 45 to 500eV electrons with helium.- Recoil ion momentum spectroscopy: a complementary technique to (e,2e) and (e,3e.- Arbitrary charged particle-impact ionisation of H and He: scaling properties of the cross sections.- Electron impact ionisation-excitation of helium: calculations using coupled channel parametric potential wavefunctions.- Democratic parameters for (e,2e) and (e,3e) kinematics.- Asymptotically exact distorted wave calculations.- New experiments needed in (e,2e.- New trends: electron impact ionisation of laser excited atoms and double ionisation by electron and photon impact.- Laser-assisted (e,2e) collisions.- (e,2e) calculations using a correlated final state.- Solid state perspective in the theory of the Auger decay.- High-performance computers in (e,2e) and (e,3e) interactions with atoms.- Energy loss and (e,2e) studies of molecules on surfaces.- Influence of Coulomb forces on the angular momenta of products in three or more fragmentary reactions.- Multiconfiguration Hartree-Fock calculation of the autoionisation resonance parameters in the (e,2e) reaction on helium atom.- Near threshold (?, 2e) experiments in the perpendicular plane.- Multicoincidence investigation of ionisation dynamics.- Coupling the coplanar (e,2e) geometry to the perpendicular plane geometry.- Double ionisation of noble gases by electron impact.- Coulomb-Born approximation forthe calculation of (e,2e) cross-sections.- In Memorium Wolfgang Hink.- Processes other than simple outer shell ionisation.- Investigation of the angular dependence of post collision interaction effects using coincidence techniques.- Relativitic (e,2e) processes under Bethe ridge conditions.- Distorted-wave calculations of triple differential cross section for inner shell ionisation.- Participants.- Contributors.
