Ma Ying-Jun

Observation of Three-Quasiparticle Doublet Bands in 123I: Possible Evidence of Chirality

A new band in the odd proton nucleus 123I is identified via in-beam γ-ray spectroscopy using the 14N+116Cd reaction. This band shows up as doublets with the previously assigned πg7/2 ⊗ (νh11/2)2 band. Possible configurations of the new band are discussed in the framework of the cranked shell model and the geometrical model. It is argued that the new band might be a chiral partner of the previously known πg7/2 ⊗ (νh11/2) band.

Search for the Chiral Band in the N =71 Odd-Odd Nucleus 126Cs

High-spin states in 126Cs are studied via the 116Cd(14N, 4n) reaction at a beam energy of 65 MeV. The sideband of the πh11/2⊗νh11/2 yrast band, a ΔI = 2 band known from previous study, is developed into a ΔI = 1 coupled structure at low spins. This sideband is assigned to be built on the same configuration as the yrast band according to the measured ratios of directional correlation of orientation and observed alignment properties. On the basis of comparisons with the previously proposed chiral doublet bands for 128,130Cs, the observed two πh11/2⊗νh11/2 bands are proposed to be candidates for chiral doublet bands in 126Cs.

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).

Band crossings and signature splitting in 159Ho

High spin states in 159 Ho were populated in the reaction 152 Sm(11 B,4n) at 60 MeV. The rotational band based on the 7/2+ [404] Nilsson configuration has been established and the rotational bands based on the 7/2- [523], 1/2+ [411] and 1/2- [541] Nilsson configurations have been extended. The neutron band crossings of the various bands and the energy signature splitting of the 7/2- [523] bands are analysed in terms of the cranked shell model.

High-Spin Level Scheme of 120I

Excited states in 120I are investigated utilizing in-beam gamma-ray spectroscopy following the 114Cd(11B,5n) reaction at 70 MeV bombarding energy. A level scheme is constructed with states up to 9 MeV. The levels are classified into several bands and their possible configurations at low spins are discussed briefly Based on the linking transitions between different bands at higher spins, the excitation energy of the previously reported T1/2 = 53 min isomer is ascertained to be 72 keV. Evidence showing the existence of an isomer at an excitation energy of 6.4 MeV is presented.

Near-Yrast Structures in Odd-Odd 122I Nucleus

Excited states of the odd-odd nucleus 122I are investigated via the fusion-evaporation reaction 116Cd(11B,5n) at a beam energy of 68 MeV. The two most strongly populated bands in 122I are observed up to excitation energies around 10.5 MeV. Their possible configurations at lower spins are assigned to πh11/2 ⊗ vh11/2 and πh11/2 ⊗ vd5/2 based on the observed population, B(M1)/B(E2) values, alignments and signature splitting. E1 transitions are observed connecting the πh11/2 ⊗ vd5/2 band to the πh11/2 ⊗ vh11/2 band, which may be evidence of octupole collectivity. Band terminations caused by the full alignment of the valence nucleons outside the 114Sn core are observed in both bands.

A New High-Spin Level Scheme of 128I

High-spin states in the odd-odd nucleus 128I are investigated via the 124Sn(7Li,3n)128I reaction at 28 and 32 MeV beam energies. A new level scheme of 128I is established up to high-spin states at Iπ = 16, including 48 levels and 72 γ transitions. The present level scheme is largely different from the one in a recent publication due to identification of several doublet and triplet γ transitions and their proper placements in the level scheme. The high-spin level structure exhibits no obvious collective properties and is possibly associated with two and multi-quasiparticle configurations.

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.

Band Structures of the Nucleus 129Cs

High-spin states in 129Cs are populated via the 122Sn (11B, 4n) reaction at beam energies of 55 and 60 MeV. Two additional bands are placed in the level scheme and the previously known bands are extended to higher spins. The results are compared to the cranked shell model calculations and to the systematics of the adjacent Cs isotpoes. One of the new bands is interpreted as the γ-vibrational band built on the πh11/2 orbital. The possible configuration for another new band is discussed. Upbend caused by (vh11/2)2 alignment is observed both in the favored and unfavored sequences of the πh11/2 configuration. The band based on the πg7/2 configuration at low spins forks around spin 17/2, and the two different S-bands are attributed to (vh11/2) and (πh11/2)2 rotational alignments, respectively.

Doublet bands in 128La and systematic features of energy separation of doublet bands observed in the A∼130 mass region

High spin states of 128La have been studied through the fusion-evaporation reaction 118Sn(14N, 4n)128La at a beam energy of 69 MeV. A positive-parity side band with the same configuration as that of the yrast band has been identified. Moreover, it is noted that the energy separation ΔE(I) = E(I)side − E(I)yrast of all doublet bands reported in odd-odd nuclei in the A~130 mass region exhibit a staggering pattern systematically, and they stagger up at even-spin and stagger down at odd-spin.