Intrinsic states, high-spin rotational bands and rotation alignment in 177Os and 179Os

doi:10.1016/0375-9474(83)90362-7

Nuclear Physics A

Volume 401, Issue 3, 13 June 1983, Pages 490-520

https://doi.org/10.1016/0375-9474(83)90362-7 Get rights and content

Abstract

Low-lying intrinsic states and their associated rotational bands have been identified in ¹⁷⁷Os and ¹⁷⁹Os. They are the mixed i_$132$ neutron states and the $12$ ⁻[521] states in ¹⁷⁷Os and ¹⁷⁹Os, as well as the $52$ ⁻[512] state in ¹⁷⁷Os and the $72$ ⁻[514] state in ¹⁷⁹Os. The $12$ ⁻ sta is assumed to be the ground state, the other intrinsic states giving rise to isomers. The in-band decay properties of the $72$ ⁻[514] band, and the i_$132$ bands show the effect of mixing. In the rotational bands in ¹⁷⁷Os a low frequency backbending anomaly is observed but no anomaly is observed in the i_$132$. band. In ¹⁷⁹Os the i_$132$ band does backbend but at a higher frequency than in the yrast bands of the even neighbours. The systematics of the backbending frequencies, and the effects of blocking, are discussed. The rotation aligned angular momentum is deduced, and a comparison made between the i_$132$ bands and the s-bands in the even neighbours. The results broadly support the identification of the s-bands with the aligned (i_$132$)² configuration.

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Nuclear Data Sheets for A = 179
2009, Nuclear Data Sheets
Nuclear structure data pertaining to all nuclei with mass number A = 179 (Yb, Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl) have been compiled and evaluated, and incorporated into the ENSDF database. This evaluation for A = 179, which considers data available by 15 November 2008, supersedes the previous complete publication (E. Browne, Nuclear Data Sheets 55, 483 (1988), cutoff September 1987) and the update-mode publication (C. Baglin, Nuclear Data Sheets 72, 617 (1994), cutoff date September 1994), as well as the subsequent evaluations of Ta, Ir and Tl by C. Baglin (literature cutoff dates January 2000, October 1998 and February 2001, respectively). The newly evaluated literature provides new Coulomb excitation data for Hf, transfer reaction data for Hf and Ta, new information on Au and Hg from α decay and significant (HI,xnγ) reaction data for Hf, Ta, Re, Au and Hg. At the time of the 1994 evaluation, no γ-ray information was available for Au or Hg; that situation has now changed dramatically, although additional work on details of the low-lying structure of Au could be instructive.
Nuclear data sheets for A = 177
2003, Nuclear Data Sheets
Bandcrossings in 171Os
1999, Nuclear Physics A
The nucleus ¹⁷¹Os has been populated using the reaction ¹¹⁶Sn(⁵⁸Ni,2pn). Four new bands are identified, and the previously known bands are extended in spin, to a maximum of $532 h ̵$ . One- and three-quasiparticle configurations are identified, and β, γ, and octupole configurations are assigned tentatively. The effects of a possible intruder configuration on the negative parity bands are tested using band-mixing calculations.
Multi-quasiparticle states and K-forbiddenness in 177W
1997, Nuclear Physics A
High-spin states in ¹⁷⁷W have been populated using the ¹⁶⁴Dy(¹⁸O,5n) reaction at a beam energy of 83 MeV. Six new high-K bands based on 3-, 5- and 7-quasiparticle excitations have been observed. Nilsson configurations for these bands are discussed, and experimental and calculated g-factors are compared. Decays of the $K^{π} = 292^{+}$ 5-quasiparticle state to the members of the $K^{π} = 72^{+}$ band have been observed. The decay rates are compared with predictions calculated within a tunneling model where the nuclear shapes are considered to change along the γ direction in the (ϵ₂, γ) deformation plane.
Identification of 181Hg and shape coexistence in odd-A Hg isotopes
1997, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
In-beam γ-ray transitions in ¹⁸¹Hg, the lightest odd-A Hg isotope known thus far, have been identified from fragment mass-γ and γ-γ coincidence measurements. Five prolate deformed rotational bands were placed in the level scheme. A decoupled band built on the strongly prolate deformed $12^{−} [521]$ ground state was observed up to $292^{−}$ . A $52^{−} [512]$ configuration is suggested for a pair of strongly coupled bands displaying no signature splitting. The other two bands are also signature partner bands. They are populated with the largest intensity and exhibit splitting. They have been associated with the mixed neutron $i_{132}$ orbitals and are proposed to decay to an $i_{132}$ isomeric state associated with an oblate state.
High-spin states in 183Hg and shape coexistence in the odd-mass mercury isotopes
1995, Nuclear Physics, Section A
High-spin states in ¹⁸³Hg have been identified using the reaction ¹⁵⁵Gd(³²S,4n). Three prolate-deformed rotational bands associated with the $12^{−} [521]$ , $72^{−} [514]$ and mixed $i_{132}$ neutron orbitals are observed, while the existence of an oblate $132^{+}$ bandhead is inferred, implying co-existing prolate and oblate nuclear shapes. A two-band mixing model used to fit the state energies of the $i_{132}$ neutron bands in ^183,185,187Hg gives parameter values which are consistent with the existence of two bands with different deformations. The B(E2) ratios of the intra- and inter-band transitions in these coexisting bands are also investigated. Many of the features can be reproduced but difficulties remain, for example the results are not consistent with the assumption of coexistence between simple prolate and oblate shapes, a problem noted previously for the even-mass isotopes. Systematics of the prolate-oblate energy differences show that the energy of the prolate well relative to the oblate well is ∼ 350 keV lower in the odd-mass isotopes than in the even-mass isotopes. Possible reasons for this are described. The nature of the first alignment in the prolate bands in the mercury isotopes is discussed within the cranked shell model.

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^†: Present address: Tandem Accelerator Laboratory Box 533 S-751 21 Uppsala, Sweden.

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Nuclear Physics A

Abstract

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Identification of <sup>181</sup>Hg and shape coexistence in odd-A Hg isotopes

High-spin states in <sup>183</sup>Hg and shape coexistence in the odd-mass mercury isotopes