Muonium in bulk fused quartz: Test case for RAHD relaxation theory

Muonium (μ ⁺ e ⁻) in bulk fused quartz is a unique system in that theμ ⁺ spin polarization (in the muonium state) relaxes almost entirely via random anisotropic hyperfine distortions (RAHD). As such, this system provides an excellent test case for a new RAHD spin relaxation theory. This theory is quantitatively compared to static zero field data and the functional characteristics in both the high field and dynamic limits are considered as well.     

Dynamical behavior of muonium on silica surfaces

The behavior of muonium on the surface of finely divided silica (amorphous SiO₂) powder (mean grain diameter 70 Å) has been studied as a function of the surface concentration of hydroxyl groups. The temperature dependence of the Mu relaxation rate in transverse field was measured for samples prepared with 0%, 50% and 70% of the surface hydroxyl groups removed over the temperature range 4 K <T < 300 K. The relaxation rate shows a distinct maximum at about 25 K and a minimum at about 16 K for all three samples, and shows a dramatic decrease below 16 K as the concentration of surface hydroxyls is reduced. A three-state nonequilibrium model describing the diffusion and trapping of muonium on the silica surface is used to interpret the data.On leave from Department of Physics, University of Saskatchewan, Saskatoon, Sask. S7N OWO, Canada.     

Coexisting holes and electrons in high-T C materials: implications from normal state transport

Normal state resistivity and Hall effect are shown to be successfully modeled by a two-band model of holes and electrons that is applied self-consistently to (i) dc transport data reported for eight bulk-crystal and six oriented-film specimens of YBa₂Cu₃O_7?δ, and (ii) far-infrared Hall angle data reported for YBa₂Cu₃O_7?δ and Bi₂Sr₂CaCu₂O_8+δ. The electron band exhibits extremely strong scattering; the extrapolated dc residual resistivity of the electronic component is shown to be consistent with the previously observed excess thermal conductivity and excess electrodynamic conductivity at low temperature. Two-band hole–electron analysis of Hall angle data suggests that the electrons possess the greater effective mass.     

Muonium reaction with ethylene on powder surfaces

The reaction rates of muonium with ethylene adsorbed on the surface of amorphous silica powder grains were measured between 6 K and 300 K. k_f values characterizing the two-dimensional surface reactions and the 2 1/2 dimensional reactions with muonium in the gas phase were obtained.