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Systematic study of multi-quasiparticle K-isomeric bands in tungsten isotopes by the extended projected shell model

Wu, X-Y, Ghorui, S, Wang, L-J, Sun, Y, Guidry, M and Walker, Philip (2017) Systematic study of multi-quasiparticle K-isomeric bands in tungsten isotopes by the extended projected shell model Physical Review C, 95 (6), 064314.

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The interplay between collective and single-particle degrees of freedom is an important structure aspect to study. The nuclei in theA ≈ 180 mass region are often denoted as good examples to study such problems because these nuclei are known to exhibit many rotational bands based on multi-quasiparticle K isomers.


A large set of high-quality experimental data on high-K isomeric states in the A ≈ 180 mass region has accumulated. A systematic description of them is a theoretical challenge as it requires a method going beyond the usual mean field with multi-quasiparticle configurations built in the shell-model basis. The K-isomer data provide an ideal testing ground for theoretical models.


The recently extended projected shell model (PSM) by the Pfaffian method is employed with a sufficiently large configuration space including up to 10 quasiparticles. The restoration of rotational symmetry which is broken in the deformed mean field is obtained by means of angular-momentum projection. With axial symmetry in the basis deformation, each multi-quasiparticle state, classified by a K quantum number, represents the major component of a rotational K band. Shell-model diagonalization in such a projected basis defines the K mixing, which is the key ingredient of the present method.


Quasiparticle structure and rotational properties of high-K isomers in even-even neutron-rich 174−186W isotopes are described. The rotational evolution of the yrast and near-yrast bands is discussed with successive band crossings. Multi-quasiparticle K isomers and associated rotational bands in each W isotope are studied with detailed quasiparticle configurations given. Electromagnetic transition properties are also studied and the calculated B(E2), B(M1), and g-factors are compared with experiment if data exist.


Many nuclei of the A ≈ 180 mass region exhibit properties of an axially symmetric shape and K is approximately a good quantum number. For such nuclei, the extended PSM assuming an axially symmetric basis but including K mixing through diagonalization of the two-body Hamiltonian is an appropriate method to study multi-quasiparticle K isomers and K violations in these states. For special examples where one finds highly K-forbidden transitions the present model needs to be further improved.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Physics
Authors :
Wu, X-Y
Ghorui, S
Wang, L-J
Sun, Y
Guidry, M
Date : 16 June 2017
Funders : STFC
DOI : 10.1103/PhysRevC.95.064314
Copyright Disclaimer : Copyright 2017 American Physical Society
Depositing User : Melanie Hughes
Date Deposited : 06 Feb 2018 11:05
Last Modified : 11 Dec 2018 11:23

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