Pressure-induced structural phase transition of iodine

The structural phase transition of iodine was observed at about 210 kbar and at room temperature by the high-pressure x-ray diffraction technique using a diamond-anvil cell and a position-sensitive detector. It was found to occur reversibly in both processes of increasing and decreasing pressure.     

Dielectric study of the alpha and beta processes in supercooled ethylene glycol oligomer-water mixtures

Broadband dielectric measurements for 65 wt % ethylene glycol oligomer (EGO)-water mixtures with one to six repeat units of EGO molecules were performed in the frequency range of 10 microHz-10 GHz and the temperature range of 128-298 K. In the case of the water-EGO mixtures with one and two repeat units of the EGO molecule (small EGO), the shape of the dielectric loss peak of the primary process is asymmetrical about the logarithm of the frequency of maximum loss above the crossover temperature, T(C). The asymmetric process continues to the alpha process at a low frequency, and an additional beta process appears in the frequency range higher than that of the alpha process below T(C). In contrast, the water-EGO mixtures with three or more repeat units of the EGO molecule (large EGO) show a broad and symmetrical loss peak of the primary process above T(C). The symmetric process continues to the beta process, and an additional alpha process appears in the frequency range lower than that of the beta process below T(C). These different scenarios of the alpha-beta separation related to the shape of the loss peak above T(C) are a result of the difference in the cooperative motion of water and solute molecules. The solute and water molecules move cooperatively in the small EGO-water mixtures above T(C), and this cooperative motion leads to the asymmetric loss peak above T(C) and the alpha process below T(C). For the large EGO-water mixtures, the spatially restricted motion of water confined by solute molecules leads to the symmetric loss peak above T(C) and the beta process below T(C).     

Electronic structure of the muonium center as a shallow donor in ZnO

The electronic structure and the location of muonium centers (Mu) in single-crystalline ZnO were determined for the first time. Two species of Mu centers with extremely small hyperfine parameters have been observed below 40 K. Both Mu centers have an axial-symmetric hyperfine structure along with a <0001> axis, indicating that they are located at the antibonding (AB(O, parallel )) and bond-center (BC( parallel )) sites. It is inferred from their small ionization energy ( approximately 6 and 50 meV) and hyperfine parameters ( approximately 10(-4) times the vacuum value) that these centers behave as shallow donors, strongly suggesting that hydrogen is one of the primary origins of n type conductivity in as-grown ZnO.     

Threshold Conditions for Bulk Second-Order Nonlinearity and Near-Surf ace Second-Order Nonlinearity in Thermally Poled Infrasil Silica

Generation of bulk second-order nonlinearity in silica glass requires higher poling temperature or longer poling time than that of near-surface second-order nonlinearity. The threshold conditions for initiating the bulk second-order nonlinearity are studied on Infrasil fused silica glass. The threshold poling time is strongly dependent on the poling temperature. The near-surface second-order nonlinearity is also studied, especially the dependence of thickness of the nonlinear layer on the poling temperature, poling voltage and poling time. Secondary-ion mass-spectroscopy measurement showed depletion of Na⁺ ions at the anodic surface. We assume there is an ionic wave during poling traveling from the anodic surface to generate the dipolar electric field that induces the near-surface second-order nonlinearity.     

Study of Muon-Catalyzed Fusion in Ortho–Para Controlled Solid Deuterium

Recently, the applicability of Penning trap mass spectrometry has been extended to nuclides with a half-life of less than one second. The mass of ³³Ar (T _1/2=174 ms) was measured using the ISOLTRAP spectrometer with an accuracy of 4.2 keV. This measurement provided a stringent test of the Isobaric Multiplet Mass Equation (IMME) at mass number A=33 and isospin T=3/2. The fast measurement cycle that shows the way to other measurements of very-short-lived nuclides is presented. Furthermore, the results of the IMME test are displayed. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Muon Science Facility at the JKJ Project

The muon science facility is one of the experimental arenas of the JKJ project, which was recently approved for construction in a period from 2001 to 2006, as well as neutron science, particle and nuclear physics, neutrino physics and nuclear transmutation science. The muon science experimental area is planned to be located in the integrated building of the facility for the materials and life science study. One muon target will be installed upstream of the neutron target in a period of phase 1. The beam line and facility are designed to allow the later installation of a 2nd muon target in a more upstream location. The detailed design for electricity, cooling water, primary proton beam line, one muon target and secondary beam lines (a superconducting solenoid decay muon channel, a dedicated surface muon channel, and an ultra slow muon channel) is underway. In the symposium, a latest status of the muon science facility at JKJ project will be reported. This revised version was published online in August 2006 with corrections to the Cover Date.