Anomalous rotational energies and transition probabilities at high spin in the ground-state band in 159Ho

doi:10.1016/0375-9474(75)90502-3

Nuclear Physics A

Volume 252, Issue 2, 10 November 1975, Pages 315-332

https://doi.org/10.1016/0375-9474(75)90502-3 Get rights and content

Abstract

Levels with spin values up to $352$ in the ground-state band of ¹⁵⁹Ho are populated when a ¹⁵⁹Tb target is bombarded with 49 MeV α-particles. The observed pattern of rotational energies is discussed within a model where a quasiparticle is coupled to a rotor with a variable moment of inertia. The analysis suggests that the core exhibits back-bending similar to the behaviour in ¹⁶⁰Er and ¹⁵⁸Dy. However, the angular velocity giving back-bending is larger than in the adjacent even nucleides uless the introduced ad hoc attenuation of the Coriolis force disappears at high spin, or more likely, unless the matrix elements of j² are also reduced. This uncertainty associated with the motion of the odd particle precludes the analysis of small effects on the back-bending mechanism due to the blocking of an $h_{112}$ orbital. The relative γ-ray intensities support the notion that g_R decreases with increasing values of spin. Furthermore, in the region of back-bending an additional drop of the E2/M1 branching ratio suggests that the B(E2) values are here reduced by about 50%.

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Cited by (21)

Microscopic insight into the study of band spectra of 158Ho and 159,161,163Ho isotopes
2016, Nuclear Physics A
The nuclear structure properties of the low-lying and excited states of Holmium isotopes have been studied within the framework of Projected Shell Model. The theoretical results are found to be in the reasonable agreement with the observed ones. The theoretical $B (M 1) / B (E 2)$ estimates of ¹⁵⁸Ho are seen to reproduce the same systematics as shown by the observed ones. However, for ^159,161,163Ho, the $B (E 2)$ transition probabilities for the ground state band have been predicted for transitions for which the experimental values are not available.
Nuclear Data Sheets for A = 159
2012, Nuclear Data Sheets
Nuclear data sheets for A = 159
2003, Nuclear Data Sheets
Nuclear data sheets for A = 159
1988, Nuclear Data Sheets
Nuclear Data Sheets for A = 159
1988, Nuclear Data Sheets
Signature-dependent ml and e2 transition probabilities in 155ho and 157ho
1984, Nuclear Physics, Section A
¹⁵⁵Ho and ¹⁵⁷Ho have been populated in the reactions ¹⁴¹Pr(¹⁸O,4n) and ¹⁴⁶Nd(¹⁵N, 4n) at 85 and 74 MeV, respectively. In both nuclei bands built on the $72$ −[523] configuration were established to spin values considerably above the first backbend. A signature dependence in the excitation energies as well as in the ratio of M1 to E2 transition rates is observed below, but not above, the backbend in both nuclei. In ¹⁵⁷Ho lifetimes were measured with the recoil-distance method. The ΔI = 2; E2 transition probabilities obtained show very little variation with either signature or spin and no irregularity at the backbend. The signature dependence and strong rise in the ratio B(M1)/B(E2) observed at the backbend in ¹⁵⁷Ho therefore must be caused by the B(M1) values. A signature dependence in the B(E2, I → I −1)/B(E2, I → I −2) ratios also found in ¹⁵⁷Ho below the backbend is mainly the result of signature dependence in the ΔI = 1 ; E2 transition rates. Qualitatively, most of the features observed can be explained by nonaxial deformations, which change from large negative to slightly positive values of γ at the backbend.

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^†: Permanent address: Accelerator Laboratory, Department of Physics, University of Helsinki, Finland.

^††: Permanent address: Nuclear Physics Institute, Praha, Czechoslovakia.

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Nuclear Physics A

Abstract

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Cited by (21)

Microscopic insight into the study of band spectra of <sup>158</sup>Ho and <sup>159,161,163</sup>Ho isotopes

Nuclear Data Sheets for A = 159

Nuclear data sheets for A = 159

Nuclear data sheets for A = 159

Nuclear Data Sheets for A = 159

Signature-dependent ml and e2 transition probabilities in <sup>155</sup>ho and <sup>157</sup>ho