Study of high-spin states in 181, 182Os

doi:10.1016/0375-9474(94)00819-9

Nuclear Physics A

Volume 587, Issue 1, 1 May 1995, Pages 111-149

https://doi.org/10.1016/0375-9474(94)00819-9 Get rights and content

Abstract

High-spin states in the nuclei ^{181, 182}Os have been populated in the $^{150} Nd(^{36} S,x n)$ reactions and studied with the ESSA30 array. The nucleus ¹⁸¹Os has also been studied at the NBI tandem accelerator using the ¹⁶⁷Er(¹⁸O,4n) reaction. The previously known bands in both nuclei have been extended to higher spins and two new side bands have been found in ¹⁸¹Os. In the latter nucleus the ground state has been established to have $I^{π} = 12^{−}$ . The extraction of the ratios of reduced transition probabilities $B(M1) B(E2)$ from branching and $E2 M1$ mixing ratios permitted configuration assignments for most of the bands in both nuclei. The analysis has been carried out within the semiclassical vector model for M1 radiation. The positive-parity yrare sequences in ¹⁸²Os and the band based on the $I^{π} = K^{π} = 232^{−}$ state in ¹⁸¹Os have been interpreted as t-bands arising from a rotation about a tilted axis. The alignment behaviour and the crossing frequencies are for most of the bands consistent with predictions of the cranked shell model.

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Diversity of shapes and rotations in the γ-soft <sup>130</sup>Ba nucleus: First observation of a t-band in the A = 130 mass region
2019, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Several new bands have been identified in ¹³⁰Ba, among which there is one with band-head spin $8^{+}$ . Its properties are in agreement with the Fermi-aligned $ν h_{11 / 2}^{2}$ , $7 / 2^{-} [523] \otimes 9 / 2^{-} [514]$ Nilsson configuration. This is the first observation of a two-quasiparticle t-band in the $A = 130$ mass region. The t-band is fed by a dipole band involving two additional $h_{11 / 2}$ protons. The odd-spin partners of the proton and neutron S-bands and the ground-state band at high spins are also newly identified. The observed bands are discussed using several theoretical models, total Routhians surfaces (TRS), tilted axis cranking (TAC), particle rotor model (PRM) and projected shell model (PSM), which strongly suggest the coexistence of prolate and oblate shapes polarized by rotation aligned two-proton and two-neutron configurations, as well as prolate collective rotations around axes with different orientations. With the new results, ¹³⁰Ba presents one of the best and most complete sets of collective excitations that a γ-soft nucleus can manifest at medium and high spins, revealing a diversity of shapes and rotations for the nuclei in the $A = 130$ mass region.
Nuclear Data Sheets for A = 182
2015, Nuclear Data Sheets
Nuclear spectroscopic information for known nuclides of mass number 182 (Yb,Lu,Hf,Ta,W,Re,Os,Ir,Pt,Au, Hg,Tl,Pb) with Z=70 to 82 and N=112 to 100 have been evaluated and presented together with adopted energies and Jπ of levels in these nuclei. No excited state data are yet available for ¹⁸²Y and ¹⁸²Lu, while only limited structure information is available for ¹⁸²Pb and ¹⁸²Tl. Rotational band structures are known for ¹⁸²Hg and ¹⁸²Au but spin–parity assignments remain largely tentative. The decays of ¹⁸²Lu, ¹⁸²Hg, ¹⁸²Au and ¹⁸²Tl are not well established. The ¹⁸²Hf isotope is of geophysical and astrophysical interest.
This evaluation supersedes previous full evaluations of A = 182 published by 2010Si13, 1988Fi05 and 1975Sc13, and a selected (mainly high–spin) update of A = 182 published by 1995Si04.
Only the Adopted properties of levels and gamma rays are presented in NDS, consult the ENSDF database at www.nndc.bnl.gov/ensdf/ for details of individual reaction and decay datasets.
Nuclear Data Sheets for A=182
2010, Nuclear Data Sheets
Nuclear spectroscopic information for known nuclides of mass number 182 (Lu,Hf,Ta,W,Re,Os,Ir,Pt,Au,Hg, Tl,Pb) with Z=71 to 82 and N=111 to 100 have been evaluated and presented together with adopted energies and Jπ of levels in these nuclei. No excited state data are yet available for ¹⁸²Lu, while only limited structure information is available for ¹⁸²Pb and ¹⁸²Tl. Rotational band structures are known for ¹⁸²Hg and ¹⁸²Au but spin-parity assignments remain largely tentative. The decays of ¹⁸²Lu, ¹⁸²Hg, ¹⁸²Au and ¹⁸²Tl are not well established. The ¹⁸²Hf isotope is of geophysical and astrophysical interest. This evaluation supersedes previous full evaluations of A=182 published by 1988Fi05 and 1975Sc13, and a selected (mainly high-spin) update of A=182 published by 1995Si04.
Nuclear data sheets for A = 181
2005, Nuclear Data Sheets
The nuclear structure and the decay data for all the isobars of A = 181 are presented in this evaluation. New levels of ¹⁸¹Hf were studied by (n,γ), (pol d, p), (d, pγ) and (²³⁸U,²³⁷U'γ) reactions. New levels of ¹⁸¹Ta were studied by (p,nγ), (p, d), Coulomb excitation and heavy ion reactions. Heavy ion reactions added information to high spin states of ¹⁸¹Re, ¹⁸¹Os and ¹⁸¹Ir. In addition, ¹⁸¹Hg and ¹⁸¹Tl structures are also studied by α–decay experiments. The present evaluation supersedes the earlier one on A = 181 by R.B. Firestone (1991Fi01), published in Nuclear Data Sheets 62, 101 (1991), and the ones on ¹⁸¹Pt, ¹⁸¹Au and ¹⁸¹Hg, by C.M. Baglin, published in Nuclear Data Sheets 87, 197 (1999), 87, 225 (1999) and 87, 239 (1999).
High-spin states, lifetime measurements and isomers in <sup>181</sup>Os
2003, Nuclear Physics A
The level scheme of ¹⁸¹₇₆Os has been investigated with the ¹⁵⁰Nd(³⁶S,5n) reaction. The low-K rotational bands built upon the 9/2⁺[624], 7/2⁻[514] and 1/2⁻[521] neutron configurations have been extended and other new bands established. The configurations of these low-K bands are discussed within the framework of the cranked-shell model. The lifetimes for some of the states in the 9/2⁺[624] and 1/2⁻[521] collective rotational bands were also measured using the Doppler Shift Attenuation method. The large deformations deduced are found to be consistent with those predicted from theoretical Total Routhian Surface calculations. These results support the idea that for these low-K states the nuclear shape is axially symmetric and allows the K quantum number to be defined and the associated K-selection rule to be upheld. This behaviour apparently contrasts with that of the higher-K states in ¹⁸¹Os.
In the higher-spin regime, two new high-K intrinsic states, with K^π=37/2⁺ and K^π=41/2⁺, were established, along with the fragmented decay of a K^π=33/2⁻ intrinsic state. The configurations and excitation energies of these experimentally determined intrinsic states are found to be in excellent agreement with theoretical calculations based on a fixed shape Nilsson model plus BCS pairing. The structures on top of these intrinsic states do, however, show very different behaviour. A relatively regular high-K rotational band was observed on top of the K^π=41/2⁺ state but not for the other newly-established intrinsic states. Theoretical configuration-constrained potential energy surface calculations suggest that the irregular transition sequence above the K^π=37/2⁺ intrinsic bandhead state, the limited excitations observed above the other intrinsic states and the observation of fragmented and non-hindered decays, are due to these configurations being subject to an appreciable γ softness. These calculations reveal that the K^π=41/2⁺ configuration is less susceptible to distortions in the γ plane than any of the other high-K states.
Calculation of strongly-coupled rotational bands in terms of the tilted axis cranking model
2003, Nuclear Physics A
Recently observed strongly-coupled rotational bands associated with the $ν[505] 112^{−}$ quasiparticle state are studied by means of a microscopic tilted axis cranking (TAC) model. The results of calculation for the routhians and the B(M1)/B(E2) ratios are investigated in the light of other existing models, i.e., the strong-coupling model and the conventional cranking model. It is demonstrated that only the TAC model can successfully reproduce these two observables at the same time. The reason of the success is clarified by making connections between these models.

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¹: Permanent address: Institute of Nuclear Research and Nuclear Energy, BG-1784 Sofia, Bulgaria.

²: Permanent address: Faculty of Physics, University of Sofia, BG-1126 Sofia, Bulgaria.

³: Present address: Yale University, New Haven, CT 06511, USA.

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Study of high-spin states in 181, 182Os

Abstract

Nucl. Phys. A

Nucl. Phys. A

Nucl. Phys. A

Phys. Rev. Lett.

Nucl. Phys. A

Nucl. Phys. A

Nucl. Phys. A

Nucl. Data Sheets

J. Phys. Soc. Japan

Bull. Acad. Sci. USSR Phys. Ser.

Nucl. Phys. A

Phys. Lett. B

Nucl. Phys.

Nucl. Phys. A

Nucl. Phys. A

Nucl. Phys. A

Study of high-spin states in ^{181, 182}Os