In-beam Mössbauer study of 57Mn implanted into a low-temperature xenon

The in-beam Mössbauer spectrum of ⁵⁷Mn implanted into a Xe solid at 14 K was measured. Four singlets were observed in the spectrum, assigned to ⁵⁷Fe^?+? (3d⁷), ⁵⁷Fe^?+? (3d⁶4s¹), ⁵⁷Fe⁰ (3d⁶4s²), and ⁵⁷Fe⁰ (3d⁷4s¹). The assignments were in agreement with calculated electron densities at nuclei reported in the literature. The β-decay of ⁵⁷Mn did not disturb the surrounding Xe lattice, showing a singlet peak, and the excited states were stabilized in the time range of the Mössbauer measurements of ~100 ns. The production mechanism was explained in terms of the reduction of ⁵⁷Mn ^x?+? and ⁵⁷Fe ^y?+? ions by free electrons in the Xe matrix.     

One-step synthesis of (1-iodovinyl) arenes from trimethylsilyl ethynylarene through iodotrimethylsilane-mediated hydroiodation

One-step access to (1-iodovinyl) arenes from trimethylsilyl ethynylarenes is described. The method is superior to a conventional multi-step approach, and is enhanced by the Sonogashira reaction that provides ready access to a variety of trimethylsilyl ethynylarenes.     

Precise measurement of magnetic moment of short-lived β-emitting nuclei 12B (Iπ= 1+, T1/2 = 20.18 ms)

The spin polarized β-emitting nuclei 12B (Iπ = 1+, T1/2 = 20.18 ms) were produced by the nuclear reaction 11B(d, p) 12B and by the selection technique of the incident deuteron energy and the 12B recoil angle following the nuclear reaction. The nuclear magnetic moment of the short-lived nuclei 12B was measured by β-NMR with the β-NMR and β-NQR setup established for the first time in China. The nuclear magnetic moment of 12B was determined to be μ = 0.99993 ± 0.00048 nm or g = 0.99993 ± 0.00048 after the precise correction of the Knight shift.     

Nuclear Spin Alignment and Alignment Correlation Terms in Mass A = 8 System

The pure nuclear spin alignments of ⁸Li and ⁸B were produced from the nuclear spin polarization applying the β-NMR method. The alignment correlation terms in the β-ray angular distribution were observed to test the G parity conservation in the nuclear β decay.     

Quadrupole Moments of Na Isotopes

The electric quadrupole coupling constants eqQ/h of ²⁰Na (I ^π = 2⁺, T _1/2 = 449.7 ms), ²¹Na (I ^π = 3/2, T _1/2 = 22.49 s) and ²⁵Na (I ^π = 5/2, T _1/2 = 59.6 s) in single crystal ZnO and TiO₂ were precisely measured by applying the β-NMR technique. The ratio of the quadrupole moments between ²⁰Na (²⁵Na) and ²¹Na was determined to be 0.728 ± 0.023 (0.011 ± 0.002).     

A Possible Nuclear Spin Dewar. Hyperfine Interactions of Short-Lived β Emitter 8Li and 12B in TiO2

It was confirmed by detecting the β-NMR of ¹²B (I ^π=1⁺, T _1/2=20.2 ms) in a TiO₂ (rutile) crystal that the nuclear spin polarization of ¹²B was totally maintained in the crystal as produced through a nuclear reaction before implantation. Two locations, site 1 and site 2, were found with the relative populations 9 and 1, respectively, and the electric field gradients (EFGs) at those sites were obtained to be q(site 1)=+(37.1±0.5)10¹⁵ V/cm², η(site 1)<0.03, q(site 2)=+(185±5)10¹⁵ V/cm² and η(site 2)=0.62±0.02. We also found that about 30% of the initial polarization of ⁸Li (I ^π=2⁺, T _1/2=838 ms) was maintained in the crystal. Since the polarizations of other β emitting nuclei, ^12,16N, ^13,19O, and ⁴¹Sc were also totally maintained in the crystal, the crystal can be a “Spin Dewar” in which many short-lived nuclides can be implanted with their polarizations totally maintained during their lifetimes for the studies not only on the electronic structure of impurities in it but also on the nuclear properties. This revised version was published online in September 2006 with corrections to the Cover Date.     

Temperature dependence of Knight shifts for 12 B in Pt

The Knight shift of a short lived β-emitting nucleus ¹²B (I = 1, T _1/2 = 20 ms) implanted into Pt has been measured as a function of temperature (140?600 K) by means of the β-NMR method. The relation between the Knight shift and the susceptibility for Pt was deduced, which shows the similar tendency to that for the case of ¹²B in Pd.     

New limit on the lepton-flavor-violating decay μ+→e+γ

We present a new result based on an analysis of the data collected by the MEG detector at the Paul Scherrer Institut in 2009 and 2010, in search of the lepton-flavor-violating decay μ(+)e(+)γ. The likelihood analysis of the combined data sample, which corresponds to a total of 1.8×10(14) muon decays, gives a 90% C.L. upper limit of 2.4×10(-12) on the branching ratio of the μ(+)→e(+)γ decay, constituting the most stringent limit on the existence of this decay to date.     

Spin-polarization of radioactive 123Ing.s. by the tilted-foil method

A spin-polarized radioactive ¹²³In (I ^π , g = 1.220(2) , T _1/2 = 5.97(5) s) beam has been successfully generated by the tilted-foil method. This nuclide is the heaviest ever polarized in its ground state by this method. Using the ISOL-based re-acceleration-type facility TRIAC, an ¹²³In_g.s. beam of 305 keV/nucleon went through a stack of 15 carbon foils with a tilt angle of 70^° , and an asymmetry of 0.76 ± 0.25% of β-decays was observed by the β-NMR technique. The asymmetry shows that the tilted-foil method combined with a re-acceleration facility is useful for producing spin-polarized beams for applications such as nuclear physics and materials science.     

Thorium and americium solubilities in cement pore water containing superplasticiser compared with thermodynamic calculations

The solubility of thorium and americium in pore water squeezed from a cement paste was investigated by a batch method from oversaturation. The cement paste was prepared by mixing ordinary Portland cement with deionised water; in some cases the deionised water contained a polycarboxylic acid–base type superplasticiser. Following solidification, pore water was squeezed from the cement paste and collected for use in the solubility experiments. The aim of these was to investigate whether there was any effect of superplasticiser on the solubility of thorium and americium in the squeezed cement pore waters. The obtained solubility values in the two squeezed pore waters (with and without superplasticiser present) were similar. Thermodynamic calculations were performed with the thermodynamic database developed by Japan Atomic Energy Agency and compared with the experimental data to verify their applicability. These results showed that the superplasticiser used in the present study after mixing with the cement paste did not have a significant effect on solubility of thorium and americium, and the thermodynamic calculations were applicable in the present system. Size distribution of colloidal species of thorium and americium was also investigated.