No abstract available

[en] Delayed muonium formation via electron transport to the positive muon in semi-insulating GaP has been studied using a muon spin rotation technique with alternating electric fields. The characteristic electric field of about 50 kV/cm suggests that formation of a ground state muonium atom proceeds through an intermediate weakly bound hydrogen-like state. Results are justified within the framework of the effective mass approximation

[en] We have investigated the quantum diffusion of interstitial muonium atoms in solid mixtures of methane with krypton at temperatures from 10 to 90 K. At sufficiently high concentrations of Kr (above about 25%) the frustration of anisotropic molecular interactions produces an orientational glass phase. Even in this highly disordered medium, muonium exhibits coherent quantum tunneling dynamics with a bandwidth only slightly reduced with respect to that in pure solid methane. The muonium diffusion is shown to be long range rather than local

[en] A new technique is introduced which combines the application of an electric field (EF) with the signal detection capabilities of radio-frequency (RF)-μSR. The power of the combined technique resides in the natural complementarity of the underlying methods. By using an EF in a semiconductor or insulator, one can modify the concentration of electrons and holes around the muon and thereby change the initial muon/muonium fractions. Simultaneous use of RF-μSR then allows for the selective detection of the resulting changes in the final states. We report the first experimental test of the EF+RF-μSR idea in semi-insulating GaAs

[en] We report direct evidence that the anomalous muonium (Mu_BC⁰) center in GaAs is formed via transport to the muon of excess electrons that are initially more than 3x10^-6 cm away

[en] Conventional understanding suggests that strong disorder inevitably causes particle localization: states with the same energy are too far apart in space for tunnelling to be effective. We present experimental evidence to the contrary: we have observed coherent tunnelling of Mu atoms in a highly disordered mixture--75% CH₄+25% Kr--which forms an orientational glass phase at low temperatures

[en] Recently, we started developing a new technique that makes possible spectroscopic studies of electric field enhanced diamagnetic states in semiconductors and other materials. This novel approach combines avoided level crossing with electric-field μSR. The first results, obtained in semi-insulating GaAs, are described in this paper

[en] In a semiconductor with a large dielectric constant and a small electron effective mass, a positive ion and an electron can form a series of very weakly bound, macroscopic-sized shallow states. We present electric field (EF)-μSR measurements on CdS, where the final muonium state has an extremely low hyperfine coupling. In strong fields (higher than E_char∼5-10 kV/cm) the muonium signal is suppressed completely. We argue that muonium formation in CdS proceeds through the intermediate shallow states mentioned above. The experimental technique of EF-μSR measurements (using pulsed muon beams at ISIS) is discussed in detail

[en] The details of muonium formation via recombination of the thermalized muon and electron are discussed on the basis of μSR experiments in condensed neon, which are interpreted in the framework of the isolated μ^+- e^- pair model. The comparison of the results in different substances is made. In this context, the limits of the model, as well as possible extra factors, which can affect muonium formation, are discussed

[en] Low-energy μSR experiments were carried out on epitaxial strained La₂CuO₄ thin films of a thickness of only 12 nm. We could determine magnetic transitions at T_N=174(3) K for La₂CuO₄ on SrLaAlO₄ and T_N=168(2) K for La₂CuO₄ on SrTiO₃