Quantum diffusion of positive muon in pure tantalum

Quantum diffusion of positive muons has been studied in high purity Ta by zero and longitudinal field muon spin relaxation techniques. We found that the muon hopping rate in Ta is more or less the same as in pure Cu (i.e., ν ≅ 105 ∼ 106 s-1), showing a characteristic temperature dependence proportional to T-α with α ranging from 2 to 0.2 below 20 K. In addition, a step-like change of the nuclear dipolar width was observed at 60 K associated with the sharp peak of hopping rate, suggesting a change of stable muon sites