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

High-resolution measurements of Auger electrons from fast, multiply ch arged projectiles are reviewed. The fundamental properties of the meth od of zero-degree Auger spectroscopy are pointed out. When electrons a re 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 overv iew is given about the atomic structure aspect, such as line energies and transition rates. Emphasis is given on the aspect of collision mec hanisms that are responsible for the production of the Auger states. T he semi-classical approximation is used to describe the excitation of the projectile by target atoms. An adequate treatment of the significa nt screening effects by the neutral target atom is outlined. At high i ncident energies, the process of single excitation in collisions of 17 0 MeV Ne7+ on various target atoms is considered. Interferences betwee n first- and second-order terms are evaluated in agreement with the ex perimental results. At intermediate energies, two electron processes s uch 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.