Elektronentemperatur im Zentrum von Ionenspuren in Metallen

Abstract

High resolution Auger-electron spectra have been measured for the interaction of swift heavy ions with metallic solids. These spectra allow for a test of the thermal-spike and Coulomb-explosion models, which describe the evolution of ion tracks in solids. The key point of this investigation is the determination of electron temperatures resulting from the energy transfer by the projectile ion. Electron temperatures have been extracted from the shapes of the Auger-line structures. Measurements have been performed for aluminium, beryllium, and several metallic glasses, resulting in electron temperatures between 10 000 and 100 000 K for Auger decay times around 10 fs. There was no significant sign of heavy-ion-track potentials for the metallic samples. Conduction band electrons do neutralize the atomic charges so fast that Coulomb explosion and the corresponding Auger-energy shifts are impossible. Thus, materials modifications inside ion tracks of metals may result only from the hot electrons described in the thermal-spike model. Furthermore, angular distributions of ion-induced Auger electrons from beryllium and aluminium have been measured for the first time and significant ion-track effects have been found. In a highly excited electron system the mean free electron path-length may be reduced. The geometry of the ion track as well as of the crystal leads then to a suppression of Auger-electron yields along specific directions. In conclusion, a significant influence of the highly charged projectile on the electronic system of metals has been determined in this work for the first time.