INCREASED ELEMENTAL SPECIFICITY OF POSITRON-ANNIHILATION SPECTRA

Positron annihilation spectroscopy (PAS) is a sensitive probe for stud ying the electronic structure of defects in solids. We show that the h igh-momentum part of the Doppler-broadened annihilation spectra can be used to distinguish different elements. This is achieved by using a n ew two-detector coincidence system to examine the line shape variation s originating from high-momentum core electrons. Because the core elec trons retain their atomic character even when atoms form a solid, thes e results can be directly compared to simple theoretical predictions. The new approach adds increased elemental specificity to the PAS techn ique, and is useful in studying the elemental variations around a defe ct site.