* 最近の総説としては、たとえば, R. Kadono, Applied Magnetic Resonance 13, 37-54 (1997)を参照。
理論的予想 vs 実験例
This picture is a summary of theoretical predictions on the temperature dependence of hopping rate in crystalline solids: a steep increase of the hopping rate is expected in insulating crystal, whereas much more moderate temperature dependence is expected in metallic environments due to the Ohmic damping of tunneling motion.
This picture shows two memorial data sets of muon diffusion in high-purity copper (Kadono et al., 1989; Luke et al., 1991) and muonium (Mu) diffusion in KCl (Kiefl et al., 1989; Kadono et al., 1990; MacFarlane et al., 1994). Note that the scale of the vertical axis is very different between these two (i.e., muonium diffusion in KCl is faster than muon in copper by orders of magnitude, indicating that the tunneling matrix element for muonium in KCl is quite large).