ZERO-DEGREE AUGER-SPECTROSCOPY IN ENERGETIC, HIGHLY-CHARGED ION-ATOM COLLISIONS

High-resolution measurements of Auger electrons from fast, multiply charged projectiles are reviewed. The fundamental properties of the method of zero-degree Auger spectroscopy are pointed out. When electrons are observed at 0-degrees, kinematic broadening effects are avoided in first order. The technique of needle ionization is presented as a tool to reduce the number of lines in complex Auger spectra. A brief overview is given about the atomic structure aspect, such as line energies and transition rates. Emphasis is given on the aspect of collision mechanisms that are responsible for the production of the Auger states. The semi-classical approximation is used to describe the excitation of the projectile by target atoms. An adequate treatment of the significant screening effects by the neutral target atom is outlined. At high incident energies, the process of single excitation in collisions of 170 MeV Ne7+ on various target atoms is considered. Interferences between first- and second-order terms are evaluated in agreement with the experimental results. At intermediate energies, two electron processes such as transfer excitation and transfer loss are discussed. Particular interest is devoted to cases where the electron-electron interaction plays an important role during the collision.