Lei Xiang-Guo

Search for the Chiral Band in the N =71 Odd-Odd Nucleus 126Cs

High-spin states in 126Cs are studied via the 116Cd(14N, 4n) reaction at a beam energy of 65 MeV. The sideband of the πh11/2⊗νh11/2 yrast band, a ΔI = 2 band known from previous study, is developed into a ΔI = 1 coupled structure at low spins. This sideband is assigned to be built on the same configuration as the yrast band according to the measured ratios of directional correlation of orientation and observed alignment properties. On the basis of comparisons with the previously proposed chiral doublet bands for 128,130Cs, the observed two πh11/2⊗νh11/2 bands are proposed to be candidates for chiral doublet bands in 126Cs.

Measured and Simulated Performance of a Four-Segmented Clover Detector

Gamma rays with energies between 80 keV and 1500 keV produced by 133Ba and 152Eu standard sources are measured with the clover detector. Relative efficiencies and add-back factors are determined in both crystals and full clover modes. The add-back characteristics have been calculated using Monte-Carlo simulation code Geant4. The simulation and measurements agree very well.

Properties of the β-Delayed Proton Decay of 147Er

The ?-delayed proton decay of 147Er is studied experimentally using the 68Ni+92 Mo reaction at a beam energy of 383 MeV. Based on a He-jet apparatus coupled with a tape transport system, the ?-delayed proton radioactivities both from the ?s1/2 ground state and the ?h11/2 isomer in 147Er are identified by proton-? coincidence measurements. By analyzing the time distribution of the 4+ ? 2+? transition in the grand-daughter nucleus 146Dy, a half-life of 1.6 ? 0.2 s is determined for the ?h11/2 isomer in 147Er. The half-life for the ground state of 147Er is estimated to be 3.2 ? 1.2 s.

The β Decay of 21N

The β-delayed neutron and γ energy spectra taken from the decay of neutron-rich nucleus 21N were measured by using the β–γ and β – n coincidence detection method. Thirteen new neutron groups ranging from 0.28MeV to 4.98MeV and with a total branching ratio of 88.7 ± 4.2% were observed and presented. One γ transition with an energy of 1222keV emitted from the excited state of 21O, and four γ transitions with energies of 1674, 2397, 2780, and 3175keV emitted from the excited states of 20O were identified in the β decay chain of 21N. The β decay half-life for 21N is determined to be 82.9 ± 1.9 ms. The uncertainty of half-life is much smaller than the previous result.

Identification of Oblate Band in Odd?Odd 184Au

High-spin states in 184Au have been populated via the 149Sm(29Si, 4n?) 184Au reaction at a beam energy of 140?MeV. Three- or higher-fold ?-ray coincidences have been measured using the multidetector array of GASP. A rotational band built on the 11? oblate ?h11/2?1??i13/2?1 structure has been newly observed, similar to those reported in 186?194Au. This result extends the knowledge of shape coexistence to the currently lightest odd?odd Au isotope.

Observation of a Possible New Isomer in 175 Ir

The neutron deficient nuclide 175Ir was produced by irradiation of 146Nd with 210 MeV 35Cl via a fusion-evaporation reaction channel. The reaction products were transported to a low-background location using a helium-jet recoil fast-moving tape-transport system for measurement. The experimental devices and data analysis method are introduced. Based on the decay-curve fitting of the β-delayed γ ray from 175Ir, realized by the least-square method, a new long-lived isomeric state of Ir is proposed and briefly discussed.

Investigation of add-back effects in a segmented Clover detector

The resolution and the summing characteristics of an EXOGAM segmented Clover germanium detector has been studied for use it in γ spectroscopic experiments. The measurements have been performed with standard radioactive sources of 152Eu, 133Ba and β-delayed γ-rays from 176Ir decay. The data analytic results, realized by software, are presented in this paper.

Properties of the β-delayed proton decay of 146Ho

The proton-rich isotope 146Ho was produced via the fusion-evaporation reaction 92Mo (58Ni, 3p1n). The β-delayed proton decay of 146Ho was studied by proton-y coincidence measurements using a He-jet tape transport system. The γ-transitions in 145Tb following the proton emissions were observed, and the β-delayed proton branching ratios to the final states in the grand-daughter nucleus 145Tb were determined. According to the relative branching ratios, the ground-state spin of 146Ho has been proposed and the possible configuration discussed.

Properties of the πh9/2⊗νi13/2 Oblate Band in 188Tl

High spin states in 188Tl have been investigated via the 157Gd(35Cl,4n) reaction at beam energy of 170 MeV. A rotational band built on the πh9/2⊗νi13/2 configuration with oblate deformation has been established. Considering the similarity between the band structure observed in odd–odd Tl nuclei, spin values have been tentatively proposed for the new band in 188Tl. The πh9/2⊗νi13/2 oblate band in 188Tl shows low-spin signature inversion, and it can be interpreted qualitatively by the two quasiparticle plus rotor model including a J-dependent p–n residual interaction.

Identification of New β-Delayed γ Rays and a Low-Spin Isomer in 176Ir

The ?+/EC decay of doubly odd nucleus 176Ir has been studied via the 146Nd(35Cl, 5n?) heavy ion fusion evaporation reaction at 210?MeV bombarding energy. With the aid of a helium-jet recoil fast tape transport system, the reaction products were transported to a low-background location for measurement. Based on the data analysis, the previously known ? rays from the decay of 176Ir are proven. Moreover, three new excited levels and ten new ? rays are assigned to 176Os. The time spectra of typical ? rays clearly indicate a long-lived low-spin isomer in 176Ir.