Guo Ying-Xiang

(EC+

Abstract: The (EC+β+) decay of 128Ce was reinvestigated in the 116Sn (16O, 4n) reaction by using a helium-jet tape transport system. The close half-lives of 128Ce and 129Ce made it difficult to separate the decay γ rays of both nuclei apart. Instead of the excitation-function measurements, both reactions of 16O+116Sn and 16O+117Sn were carried out, and from their comparisons, the decay γ rays of 128Ce were clearly told from those of 129Ce. Based on X-γ and γ-γ coincidence measurements, a detailed (EC +β+) decay scheme of 128Ce has been proposed, which revises the previous one.

\beta^{+}

A standard in-beam γ-spectroscopy experiment for 188Pt is performed via the 176 Yb(18O, 6n) reaction at beam energies of 88 and 95MeV, and the level scheme for 188Pt is established. Prolate and oblate shape coexistence has been demonstrated to occur in 188Pt by applying the projected shell model. The rotation alignment of i13/2 neutrons drives the yrast sequence changing suddenly from prolate to oblate shape at angular momentum 10h, indicating likely a new type of shape phase transition along the yrast line in 188Pt.

) decay study of

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.

^{128}

Abstract: The (EC+β+) decay of 128Ce was reinvestigated in the 116Sn (16O, 4n) reaction by using a helium-jet tape transport system. The close half-lives of 128Ce and 129Ce made it difficult to separate the decay γ rays of both nuclei apart. Instead of the excitation-function measurements, both reactions of 16O+116Sn and 16O+117Sn were carried out, and from their comparisons, the decay γ rays of 128Ce were clearly told from those of 129Ce. Based on X-γ and γ-γ coincidence measurements, a detailed (EC +β+) decay scheme of 128Ce has been proposed, which revises the previous one.

Ce

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.

Prolate and Oblate Shape Coexistence in 188Pt

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.

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

High-spin states in nucleus 139Pm have been studied using the reaction 116Cd(27Al, 4n)139Pm. Two dipole cascades have been found. Spin and parity assignments were based on the Directional Correlation of Oriented Nuclei (DCO) ratios and systematic behavior in neighboring odd-proton nuclei. The level structures of 139Pm are compared with those of the N = 78 isotone 141Eu in which two dipole bands have been confirmed as magnetic rotational bands. The close similarity between them suggests that the dipole bands in 139Pm may be magnetic rotational bands.

(EC +β+) decay study of 128Ce

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.

Measured and Simulated Performance of a Four-Segmented Clover Detector

A standard in-beam gamma-spectroscopy experiment for Au-179 has been performed via the Sm-149 (Cl-35, 5n) reaction at beam energies of 164-180 MeV Based on the analysis of the experimental results, a rotational band built on the 1/2[660](pii(13/2)) proton intruder orbital is established for Au-179 for the first time. Systematic properties of the 1/2[660](i(13/2)) band in odd-A Au nuclei are discussed, and the evolution of bandhead energy and deformation with changing neutron number are revealed.

Properties of the β-Delayed Proton Decay of 147Er

The neutron rich nucleus Os-193 was produced in the Os-192(Li-7, Li-6)Os-193 reaction. An isomeric state based on the 9/2(-)[505] Nilsson orbital was identified in the present work. The half-life of the isomeric state was extracted and discussed in terms of the K quantum number. A level scheme built on the isomeric state was proposed based on the experimental data.