Zero-field μSR and low temperature μ+ diffusivity in copper

The author reviews the history of μ+ diffusion studies in copper, with particular emphasis on the increased low-temperature diffusivity which has been known for several years now. He surveys the theory and practice of the zero-field μSR method, which has come into increasing favor in the study of muon diffusion and trapping in metals, and discusses its application to the low-temperature copper problem. (Auth.)