μ+e-Hyperfine Interactions in Quartz Crystals

ABSTRACTLongitudinal muonium spin relaxation/modulation in zero magnetic field (zf-MSR) has been used to study muonium (μ+e-) atoms in single-crystal α-quartz between 5 K and room temperature. At 6 K, three frequencies are observed, corresponding to a triaxial hyperfine matrix whose principal values are close to those observed for hydrogen atoms frozen into known sites. For intermediate temperatures the Mu atoms “hop” between sites, causing a relaxation whose rate first increases with the hop rate and then decreases due to motional narrowing. Finally, at room temperature, a single-frequency oscillation is observed, corresponding to a uniaxial motionally-averaged hyperfine interaction.