The location and diffusion of positive muons in monocrystalline samples were studied. Low-temperature results clearly showed that, as in the case of H, the muons occupied tetrahedral sites in the hexagonal close-packed lattice and produced a slightly anisotropic local expansion of the surrounding metal atoms. At higher temperatures, motional narrowing was observed due to the onset of muon diffusion, and the deduced correlation times obeyed an Arrhenius behavior at temperatures above 100K. The corresponding activation energies were 0.025eV for Sc and 0.054eV for ScH0.05. A significant deviation from Arrhenius behavior was observed in hydride samples at temperatures below 100K. This was attributed to muon trapping by H.

F.N.Gygax, A.Amato, I.S.Anderson, J.J.Rush, A.Schenck: Zeitschrift für Physikalische Chemie, 1993, 181[1-2], 119-23