Wen Shu-Xian

Structure of the Semi-decoupled 1/2[411] Band in Odd Proton Nucleus169Ta

High spin states of the odd proton-nucleus 169Ta have been populated in the reaction 155Gd(19F,5n) with beam energies of 97 MeV. Rotational band based on d3/2 proton 1/2[411] Nilsson state has been pushed up to 39/2+ in the α = 1/2 decay sequence. Its signature partner, the α = -1/2 decay sequence with four link transitions has been established and 1/2[411] band in 169Ta was reassigned to be a semi-decoupled band. The systematics of the signature splitting in the K = 1/2 bands in the rear-earth region and the accidental degeneracy conclusion given by the angular projection shell model were discussed.

Measurements of g-Factor of Rotational Levels in 83Y

The g-factors of the positive parity rotational levels up to spin I = 41/2+ in 83Y have been measured by a transient-magnetic-field ion implantation perturbed angular distribution method. The experimentally measured g-factors show the g9/2 proton alignment followed by the g9/2 neutron alignment. The measured g-factors are in good agreement with the results calculated by an empirical formula based on the cranking shell model.

Band crossings and signature splitting in 159Ho

High spin states in 159 Ho were populated in the reaction 152 Sm(11 B,4n) at 60 MeV. The rotational band based on the 7/2+ [404] Nilsson configuration has been established and the rotational bands based on the 7/2- [523], 1/2+ [411] and 1/2- [541] Nilsson configurations have been extended. The neutron band crossings of the various bands and the energy signature splitting of the 7/2- [523] bands are analysed in terms of the cranked shell model.

Rotational State g-Factors in 84Zr

The g-factors of the rotational states along the positive parity yrast band in even-even nuclei 84Zr were measured up to a spin I = 16+ by a transient magnetic field-ion implanted perturbed angular distribution method and calculated by a cranking shell model. A peak structure of the g-factors has been observed for the first time. The measured g-factors confirm the mixed configuration of proton and neutron alignments.

Lifetimes of Excited Levels in131Ce

The fusion–evaporation reaction 116Sn (19F, p3n) 131Ce at projectile energy of 95 MeV is used to populate high spin states in 131Ce. The de-exciting γ-rays are detected in γ–γ coincidence measurement with Compton-suppressed BGO-HPGe detectors. Level lifetimes of 131Ce were determined by using the Doppler shift attenuation method. The experimental results indicate that collectivity of 131Ce is reduced relative to that of 130Ce and it follows that deformation decreases with increase of the neutron number on the basis of systematic comparison of transition quadrupole moments for the light cerium isotopes.

Lifetimes of High Spin Yrast States in Odd-Proton Nucleus131Pr

Lifetimes of the high spin yrast states in the odd-proton-nucleus 131Pr have been determined by analysing the Doppler broadened line shapes for the de-exciting ?-rays following the 116Sn (19F,4n) 131Pr reaction at a bombarding energy of 95?MeV. The transition quadrupole moments extracted from the measured lifetimes exhibit a considerable reduction near the rotational frequency of 0.42?MeV, at which the J(1) and J(2) moments of inertia indicate a band crossing. The experimental result demonstrates occurrence of the nuclear shape change induced by band crossing associated with the alignment of a pair of h11/2 protons.

High-spin states in the odd-proton nucleus 135Pm

High-spin states in the odd-proton nucleus 135Pm have been investigated using the 107Ag(32S, 2p2n)135Pm reaction. Seven rotational bands have been observed in 135Pm. The yrast band based on a decoupled h11/2 proton is found to have a band crossing in ωc~0.43 MeV/. Two positive-parity bands based on the two signature components of the πg7/25/2+[413] Nilsson orbital have been observed in the main sidebands. The favoured band with (π,α) = ( + ,-1/2) has been shown to populate below the first pair of proton alignment. Both bands have shown upbend at ω1~0.26 MeV/ and ω2~0.43 MeV/. These crossing frequencies can be attributed to the decoupling of the first pair of h11/2 quasi-proton and h11/2 quasi-neutron, respectively. Four weaker bands have been observed in sidebands too. Among them, two states are possibly built on a πd5/23/2+[411] configuration. PACS: 23. 20. Lv, 25. 70. -z, 27. 60. +j

On Beam Study of 198Bi Decay

Excited nucleus 198Bi was produced via the 187Re(16O, 5n)198Bi reaction. The γ-rays following the β+ /EC (electron capture) decay of 198Bi were measured in beam by using a powerful multidetector system. Based on coincidences with the known γ-rays of 198Pb, five new transitions were identified and eight new energy levels were established for 198Pb.

Shell Structures in 91 Nb

High spin states of 91Nb are populated via the fusion-evaporation reaction 76Ge (19F, 4n)91 Nb at the beam energy of 80 MeV. The existing level scheme is modified and extended to higher spins. Its low-lying states are well described by the weakly coupling between a g9/2 proton and the even-even 90Zr core, whereas the higher level structures could be interpreted by the multi-particle excitations in the model space p(1/5/2, 2p1/2,1g9/2) n (1g9/2, 2d5/2, 1g7/2) in the framework of the shell model.

Excited States in 207Rn

Excited states in 207Rn are investigated via the 196Pt(16O,Sn)207Rn reaction at beam energies from 85 to 95 MeV using techniques of in-beam γ-ray spectroscopy. Measurements of γ-ray excitation function, x-γ and γ-γ-t coincidences are performed with ten BGO(AC)HPGe detectors. Based on these measurements, a level scheme of 207Rn, including 17 γ-rays and 18 levels, is established. Spins for most of the levels are proposed according to the measured DCO ratios. The level structure is compared with a weak-coupling calculation using the interaction energies extracted from neighbouring nuclei.