Shuxian Wen

Anomalous crossing frequency in odd proton nuclei.

A generic explanation for the recently observed anomalous crossing frequencies in odd proton rare earth nuclei is given. As an example, the proton 1/2[541] band in [sup 175]Ta is discussed in detail by using the angular momentum projection theory. It is shown that the quadrupole pairing interaction is decisive in delaying the crossing point and the changes in crossing frequency along the isotope chain are due to the different neutron shell fillings.

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.

Varied signature splitting phenomena in odd proton nuclei

Varied signature splitting phenomena in odd proton rare earth nuclei are investigated. Signature splitting as functions of [ital K] and [ital j] in the angular momentum projection theory is explicitly shown and compared with those of the particle rotor model. The observed deviations from these rules are due to the band mixings. The recently measured [sup 169]Ta high spin data are taken as a typical example where fruitful information about signature effects can be extracted. Six bands, two of which have not yet been observed, were calculated and discussed in detail in this paper. The experimentally unknown band head energies are given.

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.

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 11\hbar and 15\hbar, 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).

High-spin level scheme and decay of the 67-{mu}s isomer in {sup 142}Pm

Excited states in Pm-142 are investigated via the Te-128(F-19, 5n) Pm-142 reaction at beam energies from 75 to 95 Me V by using techniques of in-beam gamma-ray spectroscopy. Measurements of gamma-ray excitation function, X-gamma and gamma-gamma-t coincidences are performed with 10 BGO(AC)HPGe detectors. Decay of the previously known 67-mus isomer in Pm-142 is observed and added into the new level scheme. This isomer is definitely placed at the excitation energy of 2828.5keV. The spin of this isomer is suggested to be 13h according to the measured gamma-ray anisotropies.

First identification of high-spin states in Ta

The yrast band in at high-spin states is established for the first time through the reaction at a beam energy of 127 MeV. Excitation function, residual radioactivity, and , coincidences were measured. Signature inversion features of and neighbouring isotones are discussed.

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 75 MeV. 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.