High-Spin Band Structure in ¹⁶⁶Yb

Abstract

High-spin states in '66Yb have been studied via the '"Sm("0, 4n)'66Yb reaction with 80MeV I6O ions from the NBI tandem accelerator. y y coincidence data were accumulated with an array of four Ge(Li) and four NaI(TI) detectors to favour high multiplicity events. Totally about 3 X lo8 events were accumulated in the coincidence experiment. Measurements of the angular distribution of the yradiation and the conversion coefficients were furthermore performed. Four weakly populated side bands are observed besides the yrast cascade which is followed up to its 24' member. The ground state band has thus been identified to its 18' state, while the crossing Stockholm band becomes the yrast band from its 16+ member. The S-band is established from its 12+ state. The observed level energies and transition rates are well reproduced in-calculations within the particle rotor model.

Recent Nuclear Structure Studies in Rapidly Rotating Nuclei

“…Similarly, the discontinuity in the aligned angular momentum plot (upper left-hand portion of Figure 9) is just the backbend associated with the shift of the yrast sequence of 1 6 8Hf9 6 (24) to a different intrinsic confi guration. Particle-number plots for the lowest positive-parity configurations both in odd-and even-N ytterbium isotopes (31,36,55,(61)(62)(63)(64)(65)(66)(67)(68)(69)(70) and for the lowest negative-parity configuration in odd-N ytterbium isotopes 9 are compared at small and large rotational frequencies in Figure 10. The change from the linear behavior of N(J.,) with minimal configuration depen dence at small rotational frequencies to an irregular behavior dependent on the confi guration at large hw indicates a dramatic reduction of the neutron pair correlations at large rotational fr equencies.…”

“…Routhians corresponding to the lowest (n, Cl) = (+ , 0), (-,0), and ( -, 1) decay sequences in a series of even-even erbium, ytterbium, and hafnium isotopes (24,31,45,55,65,67,(69)(70)(74)(75)(76)(77)(78) are shown in Figure 11. Similar plots for a series of odd-mass ytterbium isotopes (31,36,(62)(63)(64)(65)(66)(67) are given in Figure 12.…”

Recent Nuclear Structure Studies in Rapidly Rotating Nuclei

“…Similarly, the discontinuity in the aligned angular momentum plot (upper left-hand portion of Figure 9) is just the backbend associated with the shift of the yrast sequence of 1 6 8Hf9 6 (24) to a different intrinsic confi guration. Particle-number plots for the lowest positive-parity configurations both in odd-and even-N ytterbium isotopes (31,36,55,(61)(62)(63)(64)(65)(66)(67)(68)(69)(70) and for the lowest negative-parity configuration in odd-N ytterbium isotopes 9 are compared at small and large rotational frequencies in Figure 10. The change from the linear behavior of N(J.,) with minimal configuration depen dence at small rotational frequencies to an irregular behavior dependent on the confi guration at large hw indicates a dramatic reduction of the neutron pair correlations at large rotational fr equencies.…”

Backbending in theN=96 isotones

“…The g.s. and s-bands in 164Er and 166yb are known over a wide range of spins, below and above the backbending [25][26][27][29][30][31]. In the case of ~68Hf, the experimental data, which have partly been obtained by us [34], include the yrast states up to 20 + and the yrare 14 + level; four members of the s-band with spins 14 + , 16 + , 18 + and 20 + are known above the backbending.…”

“…5), we suggest possible reasons why backbending is delaYed for the ~h9/2 proton bands in the odd -Z, N=96 isotones 16STm and 167Lu. The experimental data on the energy levels of the N =96 and 97 isotones which are used in the present paper are extracted from the following references: 164Er [25][26][27]; a65Er [28]; 165Tm [18]; 166yb [29][30][31]; 167yb [32]; 167Lu [19]; 16SHf [29,33,34]; 169Hf [13]; 17~ [35]. The lifetimes of members of the g.s.…”