Diffusion and localization of muonium in Na-doped KCl

Quantum diffusion of muonium has been studied in crystals of KCl doped with small amounts of Na using the technique of muon spin relaxation. At low temperatures the crystal volume may be divided into two parts, one where the muonium diffuses rapidly as in pure KCl and the other where the muonium is effectively localized. These results are in accordance with recent theories on quantum diffusion in inhomogeneous media which predict a volume around an impurity inside which localization occurs and outside which the particle diffuses freely. © 1996 The American Physical Society.