RESONANCE TRAPPING OF POSITRONS IN SOLIDS

Basing on a new approach to the calculations of the positron trapping rate, an attempt was made to explain the prevacancy effects observed i n positron annihilation measurements in metals. The defect in the calc ulation is represented by a complex potential: the real part of it is responsible for the scattering and the imaginary part - for the trappi ng of incoming positrons. It is shown that the resonance trapping of t he positron s-wave and p-wave at low temperature and d-wave and f-wave in prethermal regions provide substantial contributions to the trappi ng rate of positrons. The calculations were done for the point defect and for the dislocation, taking into account the thermal distribution of the positron energy and the thermal expansion of the crystal lattic e. The resonance trapping of positrons could be responsible for prevac ancy effects in metals and could help to solve some problems in the st udy of positron annihilation.