Guangsheng Li

Search for the chiral doublet bands in 122Cs

High spin states in the odd–odd nucleus 122Cs have been studied by in-beam γ-ray spectroscopy with a 107Ag(19F,1p3n) fusion-evaporation reaction at a beam energy of 85 MeV. A previously known πh11/2 ⊗ νh11/2 yrast band was confirmed and its spin I was re-examined. A ΔI = 2 band was identified, which together with another known ΔI = 2 band forms a side band of the πh11/2 ⊗ νh11/2 yrast band. The two observed πh11/2 ⊗ νh11/2 bands are proposed as a pair of chiral doublet bands in 122Cs based on a systematic comparison with those in the neighbouring odd–odd Cs isotopes, as well as the relativistic mean field and the triaxial particle-rotor-model calculations.

Observation of isomeric states in197Bi

The high-spin states in197Bi have been studied with the187Re(16O, 6n)197Bi reaction at16O energies between 85 and 105 MeV. In-beam measurements ofγ-ray excitation functions,γ-γ-t coincidences and γray angular distributions were carried out with 6 BGO(AC) HPGe detectors and one intrinsic Ge planar detector. 11 new transitions and 3 new isomers at 2089, 2357 and 1968+Δ keV with t1/2 =19.3±4.9, 53.4±20.5 and 18.0±3.1 ns., respectively, were observed, and a level scheme is established. Some differences between the present work and the previous results were found.

First identification of high spin states in160Lu

A rotational band of160Lu was identified for the first time through the144Sm(19F,3n)160Lu reaction with a beam energy of 90 MeV. A γ-γ-BGO coincidence experiment was performed using five HpGe-BGO Compton-Suppressed spectrometers and a 14 elements ball of BGO detectors. The highest spin of the band with π9/2−[514]⊗v1/2+[660] could be pushed up to 21−, and it shows the feature of an anomalous signature splitting.

High-spin states and collective band structures in the odd–odd 140Pm nucleus

The high-spin states of 140Pm have been investigated through the reaction 126Te(19F, 5n) at a beam energy of 90 MeV. A previous level scheme based on the 8− isomer has been updated with spin up to 23 . A total of 22 new levels and 41 new transitions were identified. Six collective bands were observed. Five of them were expanded or re-constructed, and one of them was newly identified. The systematic signature splitting and inversion of the yrast πh11/2⊗νh11/2 band in Pr and Pm odd–odd isotopes has been discussed. Based on the systematic comparison, two ΔI = 2 bands were proposed as double-decoupled bands; other two bands with strong ΔI = 1 M1 transitions inside the bands were suggested as oblate bands with γ ~ −60°; another band with large signature splitting has been proposed with oblate-triaxial deformation with γ ~ −90°. The characteristics for these bands have been discussed.

Signature splitting inversion and backbending in80Rb

High spin states of 80Rb are studied via the fusion-evaporation reactions 65Cu+19F, 66Zn+18O and 68Zn+16O with the beam energies of 75 MeV, 76 MeV and 80 MeV, respectively. Twenty-three new states with twenty-eight new gamma transitions were added to the previously proposed level scheme, where the second negative-parity band is significantly pushed up to spins of 22^{-} and 15^{-} and two new sidebands are built on the known first negative-parity band. Two successive band crossings with frequencies 0.51 MeV and 0.61 MeV in the alpha=0 branch as well as another one in the alpha=1 branch of the second negative-parity band are observed for the first time. Signature inversions occur in the positive- and first negative-parity bands at the spins of 11hbar and 15hbar, respectively. The signature splitting is seen obviously in the second negative-parity band, but the signature inversion is not observed. It is also found that the structure of the two negative-parity bands is similar to that of its isotone ^{82}Y. Signature inversion in the positive-parity yrast band with configuration pi g_{9/2} otimes nu g_{9/2} in this nucleus is discussed using the projected shell model (PSM).

Study of the yrast band in the doubly odd156Tm

The yrast band in the doubly odd156Tm nucleus was studied through144Sm(19F,2p5n)156Tm reaction at beam energy of 105MeV. Several high-spin states of156Tm were identified and the highest spin of the band with configurationπ7/2−[523] ⊗v1/2+[660] could be built up to spin 25ħ. The level structure shows the onset of a non- or weak collectivity which generally appears at neutron number of 87 in neutron-deficient rare-earth nuclei.

High-Spin States and Level Structure in Stable Nucleus Strontium-84

High-spin states of 84Sr are populated through the reaction 70Zn (18O, 4n) 84Sr at the beam energy of 75u2005MeV. The measurements of excitation functions, γ-γ coincidences, directional correlations of oriented states (DCO) ratios and γ-transition intensities are performed using eight anticompton HPGe detectors and one planar HPGe detector. Based on the experimental results, we establish a new level scheme of 84Sr, in which 12 new states and nearly 30 new γ-transitions are identified in the present work. The positive-parity yrast band is extended to spin Iπ = 24+, while one negative-parity band is extended to spin Iπ = 19− and it is found that the even-spin and odd-spin members in high-spin states show the nature of signature staggering. The deformation of 84Sr is studied by calculating the total-Routhian-surfaces (TRS) of positive-parity yrast states in the cranked shell model formalism.

High-Spin States in141Pm

The high-spin states of 141Pm nucleus have been studied by using in-beam γ-ray spectroscopy technology through the126Te(19F, 4n) reaction at a beam energy of 90 MeV. The previous level scheme has been extended with spin up to 49/2 ℏ. Many new levels and transitions are identified. Five collective band structures are observed. Based on systematic comparison with the neighboring nuclei, two bands with strong ΔI = 1 M1 transitions inside the bands are proposed as the oblate bands with γ~−60°, and three bands with large signature splitting have been suggested as the oblate-triaxial deformation with γ~−90°. The characteristics for these bands have been discussed.

High Spin Structure in106Pd

The high spin states of Pd have been populated through the Mo(B, 1p4n)Pd reaction using a beam energy of 60 MeV provided by the Beijing HI-13 tandem accelerator at China Institute of Atomic Energy. By analyzing the γ-γ coincidence relation and DCO raios of transitions, 3 rotational bands with 13 new states and 22 new γ transitions belonging to Pd were constructed. Bands 2 and 3 with negative parity were supposed to build on the νh11/2g7/2 and νh11/2d5/2 configuration, respectively.The high spin states of 106Pd have been populated through the 100Mo(11B, 1p4n)106Pd reaction using a beam energy of 60 MeV provided by the Beijing HI-13 tandem accelerator at China Institute of Atomic Energy. By analyzing the γ-γ coincidence relation and DCO raios of transitions, 3 rotational bands with 13 new states and 22 new γ transitions belonging to 106Pd were constructed. Bands 2 and 3 with negative parity were supposed to build on the νh11/2g7/2 and νh11/2d5/2 configuration, respectively.

Yrast Band in122I and Band Termination

High spin states of the odd-odd nucleus 122I have been investigated via the fusion-evaporation reaction 116Cd(11B, 5n) at a beam energy of 68 MeV. The yrast band is extended up to Iπ = (29+). The band termination at Iπ = (22+) reported in previous studies is confirmed and interpreted as arising from a shape change from collective prolate to noncollective oblate according to Total-Routhian-Surface (TRS) calculations. In addition, the Iπ=(29+) state is assigned to the [πh11/2(πg7/2)2]23/2-⊗[(νh11/2)3(νd5/2)2]35/2− configuration corresponding to the full alignment of all valance nucleons outside the semi-closed shell.