Che Xing-Lai

High-Spin Structure in Neutron-Rich 108Ru Nucleus

High spin states in the neutron-rich 108Ru nucleus have been studied through measuring prompt γ-ray coincidences following the spontaneous fission of 252Cf with the Gammasphere detector array. The yrast band has been confirmed. The one-phonon γ-vibrational band and the two-quasiparticle band based on the 5− level have been extended up to 13+ and 15−, respectively. In addition, two levels at 1644.8 keV and 1826.5 keV excitation energies are newly identified and proposed to be the members of a two-phonon γ-vibrational band. It is shown that the 108Ru nucleus has triaxial deformation with parameters β2~0.29 and γ = −22 degrees from the total Routhian surface calculations. The observed band crossing in the yrast band is due to the alignment of a pair of h11/2 neutrons according to the cranked shell model calculations. The possible configuration for the two-quasiparticle band has been discussed.

Collective Band Structures in Neutron-Rich 108Mo Nucleus

High spin states in the neutron-rich 108Mo nucleus are studied by measuring prompt γ-rays following the spontaneous fission of 252Cf with a Gammasphere detector array. The ground-state band is confirmed, and the one-phonon γ-vibrational band is updated with spin up to 12 . A new collective band with the band head level at 1422.4 keV is suggested as a two-phonon γ-vibrational band. Another new band is proposed as a two-quasi-proton excitation band. Systematic characteristics of the collective bands are discussed.

Ab Initio Study on Structural and Magnetic Properties of Ni-Pd and Ni-Pt Linear and Zigzag Nanowires

Employing the accurate frozen-core full-potential projector augmented-wave method, the self-consistent electronic structure calculations were carried out on pure Ni, Pd, Pt and mixed Ni-Pd and Ni-Pt free-standing linear and zigzag nanowires. The bond lengths for all these systems are generally increased as their structures change from the linear to the zigzag chain. The bond lengths for Ni-Pd and Ni-Pt wires are in between the values of corresponding pure system and the bond angles around 60° suggesting the possible formation of Ni-Pd and Ni-Pt bimetallic materials. In mixed Ni-Pd and Ni-Pt chains, the Ni, Pd, and Pt atoms have quite high local magnetic moments. The calculations suggest that the magnetic moments in linear nanowires are generally larger than the ones of corresponding zigzag nanowires. It is found that there is hybridization between Ni 3d and Pd 4d, Ni 3d and Pt 5d states, which may significantly affect structural stability and magnetism of Ni-Pd and Ni-Pt nanowires.

Extended collective bands in neutron-rich 109 Ru *

Levels in the neutron-rich 109Ru have been studied by observing the prompt γ-rays following the spontaneous fission fragments of 252Cf. The ground state band and the negative parity bands have been confirmed and extended. A positive parity band with the band head level at 332.5 keV is newly identified and suggested as a single-neutron excitation band built on the 7/2+[404] Nilsson orbital. Some structural characteristics of these bands are discussed.

Search for chiral bands in A ∼ 110 neutron-rich nuclei

High spin states in A～110 neutron-rich 106Mo, 110Ru and 112Ru nuclei have been reinvestigated by measuring the prompt γ-rays from the spontaneous fission of 252Cf. Two similar sets of bands are observed to high spins in each of three nuclei. Through analyzing of characters of the band structures, the chiral doublet bands are suggested in 106Mo, 110Ru and 112Ru.

Two-Quasiparticle Bands and Isomers in 98Sr

Rotational bands in neutron-rich 98Sr nucleus have been investigated by measuring high-fold prompt γ-ray coincidence events of the spontaneous fission of 252Cf with the Gammasphere detector array. A deformed K = 3 band built on the 1838 keV level has been confirmed and extended. Another deformed K = 6 band based on the 2535 keV level has been established. Both the bands originate most probably from the ν9/2[404]⊗ν3/2[411] two-quasiparticle configuration with Ω = |Ω1−Ω2| and Ω = |Ω1+Ω2|, respectively. Based on the delay-coincidence measurements, the half-lives for the K = 3 and K = 6 band head levels have been obtained to be 13±3 ns and 4.5±1.0 ns, respectively.

High spin states in neutron-rich 106Tc nucleus

The high spin states of the neutron-rich odd-odd 106Tc nucleus have been reinvestigated by observing prompt γ-rays from the spontaneous fission of 252Cf. A previously known collective band is confirmed and expanded, and a new collective band is newly identified. Several levels in previous report in 106Tc are reexamined and they belong to the members of a band in 107Tc. The total Routhian surface (TRS) calculations show that the 106Tc has triaxial shape. The spins and parities as well as the configurations for these bands have been tentatively assigned according to the analysis of the angular momentum alignments.

High spin band structure in 139Nd

High-spin states in 139Nd nucleus have been reinvestigated with the reaction 128Te (16O, 5n) at a beam energy of 90 MeV. The level scheme has been expanded with spin up to 47/2 ħ. At the low spin states, the yrast collective structure built on the vh11/2−1 multiplet shows a transitional shape with γ ≈ 32° according to calculations of the triaxial rotor-plus-particle model. Three collective oblate bands with γ ~ −60° at the high spin states were identified for the first time. A band crossing is observed around ħω ~0.4 MeV in one oblate band based on the 25/2− level.

Search for Double γ-Vibrational Bands in Neutron-Rich 105Mo Nucleus

Levels in the neutron-rich 105Mo nucleus have been investigated by observing prompt γ-rays following the spontaneous fission fragments of 252Cf with the Gammasphere detector array. The yrast band has been confirmed and updated. The other two collective bands with the band head levels at 870.5 and 1534.6 keV are newly observed, and they are suggested as the candidates for one-phonon K = 9/2 and two-phonon K = 13/2 double γ-vibrational bands, respectively. Systematic characteristics of these bands have been discussed.