Lattice Location of Nuclear Probes by Electron and Positron Channeling

Abstract

The angular dependence of the emission yields of electrons and positrons emitted from radioactive probes implanted into single crystals was first investigated by Uggerhoj.1 The channeling effect of electrons, emitted from substantial lattice sites, is responsible for enhanced emission yields in the directions of crystal axes or planes. Positrons, on the other hand, show pronounced channeling peaks, if emitted from interstitial sites and blocking dips, if emitted from substantial lattice sites as shown for a ‹110› direction in a 112m In implanted Mo crystal (Fig. 1). In an early paper2 Uggerhoj and Andersen suggested that this effect may be used as a method for the localization of foreign atoms in single crystals. From the emission yields observed for different low index crystal directions, the lattice site occupancy of the emitter atoms can be determined.