Jing-ye Zhang

Empirical p-n interactions: global trends, configuration sensitivity and N=Z enhancements

Abstract Empirical proton-neutron (p-n) interaction strengths are extracted for all nuclei with well-known binding energies. Particularly large interaction strengths are noted for N=Z nuclei: they result primarily from the T=0 component of the interaction and are discussed in terms of both schematic and realistic shell model calculations. Also, the observed micro-structure of the p-n interaction in doubly magic and deformed regions sheds light on both the orbit sensitivity and on the role of monopole and quadrupole components of the p-n interaction.

Aligned νi132 bands coupled to different shapes in 186Hg

Abstract The structure of 186Hg has been studied through the 156Gd(34S, 4n) reaction. Three bands with even spin and parity are observed; two of them are established up to high spin and are found to cross with little interaction at I= 16+. Cranked shell model calculations suggest that these two bands can be associated with a decoupled ν i 13 2 pair based on a prolate and on an oblate or triaxial shape, respectively.

Single-particle and collective motion for proton-rich nuclei in the upper pf shell

Based on available experimental data, a new set of Nilsson parameters is proposed for proton-rich nuclei with proton or neutron numbers 28{<=}N{<=}40. The resulting single-particle spectra are compared with those from relativistic and nonrelativistic mean field theories. Collective excitations in some even-even proton-rich nuclei in the upper pf shell are investigated using the projected shell model with the new Nilsson basis. It is found that the regular bands are sharply disturbed by band crossings involving 1g{sub 9/2} neutrons and protons. Physical quantities for exploring the nature of the band disturbance and the role of the 1g{sub 9/2} single-particle are predicted, which may be tested by new experiments with radioactive beams. (c) 2000 The American Physical Society.

Systematics of g factors of 2+1 states in even-even nuclei from Gd to Pt : A microscopic description by the projected shell model

The systematics of g factor of the first excited 2{sup +} state vs neutron number N is studied by the projected shell model. The study covers the even-even nuclei of all isotopic chains from Gd to Pt. g factors are calculated by using the many-body wave functions that well reproduce the energy levels and B(E2)s of the ground-state bands. For Gd to W isotopes the characteristic feature of the g factor data along an isotopic chain is described by the present model. Deficiency of the model in the g factor description for the heavier Os and Pt isotopes is discussed.

Extending the region of triaxial superdeformation: Candidate TSD bands in 174Hf

Abstract Three, possibly four, regularly spaced rotational bands with large dynamic moments of inertia have been identified in 174 Hf. Their properties are consistent with known triaxial superdeformed bands of the Lu/Hf region. Calculations predict substantial triaxial deformation ( γ ≈±17°) for 174 Hf structures with deformation ϵ 2 ≈0.45, despite the fact that 174 Hf is eight neutrons away from the previously established N =94 triaxial superdeformed gap. Shell gaps at N =100 and 106 with γ ⩾15° are predicted for ϵ 2 ≈0.45, and are most likely responsible for the calculated TSD minima in 174 Hf.

Nature of excited 0+ states in 158Gd described by the projected shell model

Excited 0+ states are studied in the framework of the projected shell model, aiming at understanding the nature of these states in deformed nuclei in general, and the recently observed 13 excited 0+ states in 158Gd in particular. The model, which contains projected two- and four-quasiparticle states as building blocks in the basis, is able to reproduce reasonably well the energies for all the observed 0+ states. The obtained B(E2) values however tend to suggest that these 0+ states might have a mixed nature of quasiparticle excitations coupled to collective vibrations.

ODD-PARITY BANDS OF 108, 110, 112Ru

Two similar sets of odd-parity bands are observed in each of three even–even neighbors, 108, 110, 112Ru, from a study of prompt spontaneous-fission gamma rays at Gammasphere. A careful study of the odd-parity levels of these nuclei shows evidence for the features of chiral doubling. Comparisons are made with reported other candidates for chiral doubling.

Theoretical Constraints for Observation of Superdeformed Bands in the Mass-60 Region

The lightest superdeformed nuclei of the mass-60 region are described using the projected shell model. In contrast to the heaviest superdeformed nuclei where a coherent motion of nucleons often dominates the physics, it is found that alignment of g{sub 9/2} proton and neutron pairs determines the high spin behavior for superdeformed rotational bands in this mass region. It is predicted that, due to the systematics of shell fillings along the even-even Zn isotopic chain, observation of a regular superdeformed yrast band sequence will be unlikely for certain nuclei in this mass region. {copyright} {ital 1999} {ital The American Physical Society}

Competing shapes in light Tl nuclei

In-beam γ-ray spectroscopic experiments have been performed on 191Tl, 189Tl, and 187Tl, and multiple band structures are established. These enable a study of the shape competition in the transitional region below the Z = 82 gap. Among the structures observed for the first time in odd-A Tl are bands built on the low-K prolate πh9/2, low-K oblate πh11/2, and perhaps high-K oblate πi13/2 excitations.

Shell structure in empirical p-n interactions: comparison with Nilsson and shell model calculations

Abstract Calculations of the variations of residual proton-neutron (p-n) interaction matrix elements for three different mass regions are presented within the frameworks of two approaches, the Nilsson and shell models, which differ substantially in the basis states and interactions used. The excellent agreement obtained with experiment in both approaches points to the simplicity of the underlying physics in terms of orbital overlap arguments.