Plastic deformation, vacancy diffusion, and vacancy delocalization in bcc 3He.

The plastic deformation of bee 3He crystals has been studied near the melting curve, in the temperature range 0.65 K :::; T:::; 1.17 K, and for strain rates, E, from 2X 10to 2X 10sec-I. The resulting relations between strain rate and stress, at a given temperature, are accounted for in terms of dislocation climb and vacancy diffusion in the solid He. The temperature dependence of the strain rate at a given stress indicates that a nonclassical mechanism underlies the deformation process. The vacancy diffusion coefficient in bee 3He, as a function of temperature, is deduced from these results, and an energy bandwidth for delocalized vacancies of 0.24±0.05 K is obtained through a fit to theoretical predictions.