Li Guang-Sheng

Lifetime measurements in chiral nucleus 130Cs

The level lifetimes in partner bands of 130Cs have been measured using the Doppler Shift Attenuation method. The high-spin states of 130Cs were populated via fusion evaporation reaction 124Sn(11B,5n)130Cs at a beam energy of 65 MeV. The absolute M1 and E2 transition probabilities have been deduced. The results indicate that the partner bands of 130Cs manifest the chiral properties.

Electromagnetic Transition Strengths and New Insight into the Chirality in 106Ag

Excited states in 106Ag are populated through the heavy-ion fusion evaporation reaction 100Mo(11 B,5n)106 Ag at a beam energy of 60 MeV. Lifetimes are measured for transitions of the two negative-parity rotational bands in the nucleus 106 Ag. The reduced transition probabilities show a great difference between the two bands. The staggering of the B(M1) and B(M1)/B(E2) values with spin are not observed. The bands are identified to be built on two distinct quasiparticle configurations. These results are contrary to an earlier suggestion that the pair of bands in 106 Ag are chiral doublet bands.

Quest for Chirality in 107 Ag

High spin states in 107Ag have been studied via the 100Mo(11B, 4n)107Ag reaction at a beam energy of 60 MeV on the HI-13 tandem accelerator at the China Institute of Atomic Energy. By analyzing the gamma-gamma coincidence and their DCO ratios, a new level scheme of 107Ag is presented. The structures for the newly constructed bands are briefly discussed and tentatively assigned to be chiral doublet bands.

New band structures in 107Ag

High spin states in 107Ag are studied via the 100Mo(11B, 4n)107 Ag reaction at an incident beam energy of 60 MeV. Prompt γ-γ coincidence and DCO ratios are measured by the detector arrays in CIAE. The level scheme has been updated and a new negative band belonging to 107Ag is identified. The new negative side band has been constructed and its configuration is tentatively assigned to πg9/2 ⊗ νh11/2(g7/2/d5/2).

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.

Lifetime Measurement of the Low Lying Yrast States in 189Pt

High-spin states in 189Pt are populated through the heavy-ion fusion-evaporation reaction176Yb (18O, 5n)189Pt at 87MeV beam energy. An array consisting of 13 HPGe detectors is used in conjunction with the plunger device in CIAE. The lifetimes of two levels in the yrast band are determined by using the recoil distance Doppler shift method. The transition quadrupole moments Qt are extracted. The results show that the state has a much larger Qt value than that of the ground state, whereas the value deceases quickly with spin increasing. This may contribute to the shape driving effect of the quasi-neutron from the i13/2 orbital.

The g-factors and magnetic rotation in 82Rb

The g-factors of the intra-band states 12, 13, 14, 15 in a magnetic-rotational band built on the 11 state in 82Rb are measured for the first time by using a transient magnetic field-ion implantation perturbed angular distribution (TMF-IMPAD) method. The magnetic-rotational band in 82Rb is populated by the 60Ni(27Al,4pn)82Rb reaction, and the time-integral Larmor precessions are measured after recoil implantation into a polarized Fe foil. The calculation of g-factors is also carried out in terms of a semi-classical model of independent particle angular momentum coupling on the basis of the four-quasiparticle configuration π(g9/2)2 ⊗ π(p3/2, f5/2) ⊗ ν (g9/2). The measured and calculated g-factors are in good agreement with each other. The g-factors and deduced shear angles decrease with the increase of spin along the band. This clearly illustrates the shear effect of a step-by-step alignment of the valence protons and neutrons in magnetic rotation. The semi-classical calculation also shows that the alignment of the valence neutron angular momentum is faster than that of the valence protons, which results in a decrease of g-factors with increasing spin. The present results provide solid evidence of the shear mechanism of magnetic rotation.

Clarification of Confusion in Level Scheme of 124Cs

Low-lying and high-spin states of 124Cs are studied through the 116 Sn(11 B,3n)124 Cs reaction at a beam energy of 45 MeV. Several new linking transitions are observed, including three transitions between the yrast and πh11/2 ⊗ νd3/2 bands and two transitions between the yrast and πh11/2 ⊗ ν(d5/2, g7/2) bands. These transitions fix the excitation energy of the yrast band and its decay path, and confirm the existence of eight E1 linking transitions between the yrast and πh11/2 ⊗ ν(d5/2, g7/2) bands observed before. These E1 linking transitions infer the octupole correlation in Cs. The decay paths of the yrast band are investigated, and discrepancies in the level scheme of 124Cs in the latest two studies are clarified. The reason for the discrepancies is discussed. A new decoupled band is established and temporarily assigned as the unfavored signature partner of πh11/2 ⊗ νd3/2 configuration.

Shape evolution and test of the critical-point symmetry X(5) in 176Os

The lifetimes of excited states in the yrast band of 176Os have been measured up to I = 20ħ level using the Doppler shift attenuation method. The high-spin states of 176Os were populated via fusion evaporation reaction 152Sm(28Si,4n)176Os at a beam energy of 140 MeV. The results support an X(5) structure for 176Os at low spin. This structure disappears at high spin and shows a symmetry rotor character. The shape change of 176Os is similar to that of 178Os.

High-spin states in 128I

The high-spin states in 128I have been studied by using in-beam γ-ray spectroscopy with the 124Sn(7Li,3n)128I reaction at beam energies of 25, 28 and 42 MeV. A new level scheme including 20 new levels and 27 new γ-transitions for 128I has been established preliminarily.