More than thirty bands in 177Re

doi:10.1016/0375-9474(95)00187-6

Nuclear Physics A

Volume 591, Issue 2, 21 August 1995, Pages 265-322

https://doi.org/10.1016/0375-9474(95)00187-6 Get rights and content

Abstract

The level scheme of ¹⁷⁷Re has been extended extensively, with fragments of more than thirty bands, characterised by a given signature, observed. Alignments at low frequency in one-quasiparticle bands are interpreted as deformation effects and compared with the predictions of cranking calculations. The previously assigned one-quasiparticle $π i_{132}$ band is shown to be a mixture of three-quasiparticle and vibrational character. The non-observation of the one-quasiparticle $π i_{132}$ band is explained as being due to crossings of its s-band by competing bands. A number of high-K bands are also reported, including five- and seven-quasiparticle bands. Configuration assignments for these bands are aided by comparing experimental g_κ values with “effective” g_κ values, calculated with a semi-classical expression taking Coriolis mixing into account. The population of the yrast band was observed to oscillate with every four units of spin.

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Table of three-quasiparticle rotational bands in deformed nuclei, 153 ≤ A ≤ 187
2006, Atomic Data and Nuclear Data Tables
The experimentally observed level structures based on three-quasiparticle (3qp) states are classified according to their intrinsic structures, and other properties are deduced from measurements such as B(M1)/B(E2) ratios, |g_K − g_R| values, lifetimes, etc. The present table lists data for a total of 168 such structures which have been extracted from the literature for 55 nuclides in the mass region A = 153–187 (Z = 63–78, N = 88–112), with the majority of these bands in the A = 180 region (28 bands in seven Re isotopes alone). Nuclear models used for the interpretation of 3qp structures, generalization of the Gallagher–Moszkowski (GM) rules to 3qp states, and high-spin features such as t-bands, high-K isomers, signature splitting, signature inversion, alignment, etc., are discussed briefly. The literature cutoff date for extraction of data for known 3qp structures is July 15, 2005.
Test of deformation driving effects in 179Re
2003, Nuclear Physics A
Lifetimes of the high spin states of ¹⁷⁹Re have been measured by the recoil distance technique. The high spin states in ¹⁷⁹Re were populated by the fusion evaporation reaction ¹⁶⁵Ho(¹⁸O, 4n)¹⁷⁹Re at a beam energy of 82 MeV. The deformation obtained from these measurements for the $h_{92}$ configuration (β₂ ∼ 0.25) is found to be ∼ 14% higher than the deformation for the $d_{52}$ configuration (β₂ ∼ 0.22). This higher deformation for the $h_{92}$ configuration compared to the $d_{52}$ configuration, confirms its deformation driving nature. Calculations using the cranked Hartree - Fock - Bogoliubov are done for the two configurations and they provide a qualitative description of the experimental observations.
Nuclear data sheets for A = 177
2003, Nuclear Data Sheets
First observation of excited structures in neutron-deficient 179Hg: Evidence for multiple shape coexistence
2002, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Excited structures in the neutron-deficient nucleus ¹⁷⁹Hg have been established for the first time using the Gammasphere spectrometer in conjunction with the fragment mass analyzer. Competing states originating from three different minima associated with nearly spherical, oblate, and prolate deformations were found. This result can be contrasted with the situation in heavier odd-mass Hg isotopes where only two minima (oblate and prolate) have been seen. The implications of these three shapes at low spin and excitation energy are discussed in the general context of shape coexistence in this mass region.
Multi-quasiparticle states and K -forbidden transitions in 183Os
2001, Nuclear Physics A
High-spin states in ¹⁸³Os have been studied using the ¹⁷⁰Er(¹⁸O, 5n) reaction at a beam energy of 85 MeV. Nine rotational bands based on 1-, 3-, 5- and 7-quasiparticle excitations have been observed. Nilsson configurations are assigned for the newly observed bands using g-factors deduced from M1/E2 branching ratios within the bands. In addition, two isomers with K^π=(43/2⁺) and (43/2⁻) have been identified. The K^π=(43/2⁺) isomer decays directly to the K^π=9/2⁺ ground-state band with a large difference in the K quantum number, ΔK=17. The decay rates are discussed in terms of a tunneling model where high-K (isomeric) and low-K states interact via fluctuations towards triaxial nuclear shapes.
General properties of the πh<inf>9/2</inf>[541]1/2- configuration and level scheme of 165Tm
2001, Nuclear Physics A
¹⁶⁵Tm has been studied through the reactions ¹⁵⁰Nd(¹⁹F, 4n), E_beam=85 MeV and ¹⁵⁴Sm (¹⁵N, 4n), E_beam=70 MeV. The level scheme has been extended to spin 71/2⁻ℏ, and four new bands have been added. Two are assigned to the K=17/2, three-quasiparticle configurations, π[523]7/2⁻⊗ν[642]5/2⁺⊗ν[523]5/2⁻ and π[404]7/2⁺⊗ν[642]5/2⁺⊗ν[523]5/2⁻, and the remaining two are assigned to γ-vibrations coupled to an h_9/2 proton. Lifetimes of high-spin states in the [541]1/2⁻ and [411]1/2⁺ bands have been measured using DSAM techniques, allowing transition quadrupole moments to be deduced. Furthermore, crossings between the [541]1/2⁻ and [523]7/2⁻ bands and between the [411]1/2⁺ and [404]7/2⁺ bands are analysed with a band-mixing calculation to obtain the quadrupole moments of the [523]7/2⁻ and [404]7/2⁺ bands. While the [523]7/2⁻, [411]1/2⁺ and [404]7/2⁺ bands all have similar deformations, the [541]1/2⁻ band has a quadrupole moment approximately 15% larger. The relative deformations are in good agreement with diabatic potential energy surface calculations performed using the code “Ultimate Cranker”. The experimental crossing frequency, due to the alignment of i_13/2 neutrons, is found to be delayed in the [541]1/2⁻ band compared to the other bands. This is a universal feature in the rare-earth region, and extensive systematic Cranked Shell Model calculations have been performed to predict deformations and crossing frequencies for nuclei in the region. The model is unable to reproduce the full delay in crossing frequency, confirming that deformation alone is not responsible for the shift.

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¹: Present address: Department of Physics, University of Lund, S-223 62 Lund, Sweden.

²: Present address: ISKP, University of Bonn, Nussalle 14–16, D-53115 Bonn, Germany.

³: Present address: H. Niewodniczanski Institute of Nuclear Physics, ul. Radzikowskiego 152, 31–342 Cracow, Poland.

⁴: Present address: Oliver Lodge Laboratory, University of Liverpool, P.O. Box 147, Oxford Street, Liverpool L69 3BX, UK.

⁵: Present address: Niels Bohr Institute, University of Copenhagen, Tandem Accelerator Laboratory, DK-4000 Roskilde, Denmark.

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Nuclear Physics A

Abstract

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Table of three-quasiparticle rotational bands in deformed nuclei, 153 ≤ A ≤ 187

Test of deformation driving effects in <sup>179</sup>Re

Nuclear data sheets for A = 177

First observation of excited structures in neutron-deficient <sup>179</sup>Hg: Evidence for multiple shape coexistence

Multi-quasiparticle states and K -forbidden transitions in <sup>183</sup>Os

General properties of the πh<inf>9/2</inf>[541]1/2<sup>-</sup> configuration and level scheme of <sup>165</sup>Tm