Magnetic properties of Yb2Mo2O7 and Gd2Mo2O7 from rare earth Mossbauer measurements

Using 170-Yb and 155-Gd Mossbauer measurements down to 0.03K, we have examined the semiconducting pyrochlore Yb2Mo2O7 where the Mo intra-sublattice interaction is anti-ferromagnetic and the metallic pyrochlore Gd2Mo2O7 where this interaction is ferromagnetic. Additional information was obtained from susceptibility, magnetisation and 172-Yb perturbed angular correlation measurements. The microscopic measurements evidence lattice disorder which is important in Yb2Mo2O7 and modest in Gd2Mo2O7. Magnetic irreversibilities occur at 17K in Yb2Mo2O7 and at 75K in Gd2Mo2O7 and below these temperatures the rare earths carry magnetic moments which are induced through couplings with the Mo sublattice. In Gd2Mo2O7, we observe the steady state Gd hyperfine populations at 0.027K are out of thermal equilibrium, indicating that Gd and Mo spin fluctuations persist at very low temperatures. Frustration is thus operative in this essentially isotropic pyrochlore where the dominant Mo intra-sublattice interaction is ferromagnetic.Comment: 9 pages, 9 figure

Angular distributions of rays from 210bi produced in 208 pb+208pb deep-inelastic reactions

The high-spin yrast structure of the 210Bi nucleus was investigated using -ray coincidence spectroscopy following deep-inelastic reactions in the 208Pb+208Pb system. Cascades of rays following the decay of a new isomer were identified. Spin-parity assignments to the states known from previous studies as well as to newly located excitations were made based on the measured angular distributions of rays combined with a transition conversion coefficient analysis

Neutron single particle structure in Sn131 and direct neutron capture cross sections

Recent calculations suggest that the rate of neutron capture by Sn130 has a significant impact on late-time nucleosynthesis in the r process. Direct capture into low-lying bound states is expected to be significant in neutron capture near the N=82 closed shell, so r-process reaction rates may be strongly impacted by the properties of neutron single particle states in this region. In order to investigate these properties, the (d,p) reaction has been studied in inverse kinematics using a 630MeV beam of Sn130 (4.8MeV/u) and a (CD 2) n target. An array of Si strip detectors, including the Silicon Detector Array and an early implementation of the Oak Ridge Rutgers University Barrel Array, was used to detect reaction products. Results for the Sn130(d, p)Sn131 reaction are found to be very similar to those from the previously reported Sn132(d, p)Sn133 reaction. Direct-semidirect (n,γ) cross section calculations, based for the first time on experimental data, are presented. The uncertainties in these cross sections are thus reduced by orders of magnitude from previous estimates. © 2012 American Physical Society

One-neutron transfer study of 135Te and 137Xe by particle-γ coincidence spectroscopy: The ν1i13/2 state at N = 83

Additional information is reported on single-neutron states above the doubly closed-shell nucleus 132Sn. A radioactive ion beam of 134Te(N=82) at 565 MeV and a stable ion beam of 136Xe(N=82) at 560 MeV were used to study single-neutron states in the N=8