Search

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.

High-spin states in 122Ba have been investigated in the 107Ag(19F, 4n) reaction by in-beam γ-ray spectroscopic methods. The ground-state band has been observed with spin up to 20 and a negative-parity band is identified with spin state up to 19. A band-crossing in the yrast band is observed at a rotational frequency of ω≈ 0.36 MeV and, in accordance with cranked shell model calculations, is interpreted as arising from the alignment of two h11/2 protons. Strong E1 transitions between the negative-parity and the yrast bands have been observed, which are proposed as possible evidence for octupole correlations.

High spin states in 137Ce have been studied by using the heavy-ion induced reaction 124Sn(18O, 5n) carried out at China Institute of Atomic Energy. Partial level scheme with spin up to (43/2-), including a high spin collective rotational band observed for the first time, has been established. The collective band shows the properties similar to those oblate bands with ? ~ -60? in neighboring nuclei and probably originates from the five quasi-particle configuration ?s1/2 ? [?h11/2]2 ? ?g7/2 ? ?h11/2. The characteristics of this oblate band have been discussed.

High spin states in neutron-rich odd-N 145Ba nucleus have been investigated from study of prompt γ-rays in spontaneous fission of 252Cf. The alternating parity bands are identified indicating octupole deformation with simplex quantum number s = -i. The ground state band shows signature splitting and inversion at low spin. These collective band structures exhibit the competition and co-existence between symmetric and asymmetric shapes.

High spin states in 138Ce have been investigated following heavy-ion induced reactions carried out at the China Institute of Atomic Energy, Beijing. Two collective rotational bands were established for the first time. These two bands show oblate deformation with γ = -60° and probably originate from the four quasiparticle configurations πg7/2 ⊗ πh11/2 ⊗ νh11/2 ⊗ νd3/2 and πg7/2 ⊗ πh11/2 ⊗ [νh11/2]2, respectively. These oblate bands exhibit strong M 1 transitions, no signature splitting and different moments of inertia from those of prolate bands.

High spin states in neutron-rich odd-{ital Z} {sup 143,145}Ba nuclei have been investigated from the study of prompt {gamma} rays in the spontaneous fission of {sup 252}Cf by using {gamma}-{gamma}- and {gamma}-{gamma}-{gamma}- coincidence techniques. Alternating parity bands are identified for the first time in {sup 145}Ba and extended in {sup 143}Ba. A new side band, with equal, constant dynamic, and kinetic moments of inertia equal to the rigid body value, as found in superdeformed bands, is discovered in {sup 145}Ba. Enhanced E1 transitions between the negative- and positive-parity bands in these nuclei give evidence for strong octupole deformation in {sup 143}Ba and in {sup 145}Ba. These collective bands show competition and coexistence between symmetric and asymmetric shapes in {sup 145}Ba. Evidence is found for crossing M1 and E1 transitions between the s=+i and s={minus}i doublets in {sup 143}Ba. {copyright} {ital 1999} {ital The American Physical Society}