Volume 132, Number 3, November 2020
|Number of page(s)||7|
|Published online||29 December 2020|
On the importance of np-pairs in the isovector pairing model
1 Department of Physics, Liaoning Normal University - Dalian 116029, China
2 Department of Physics and Astronomy, Louisiana State University - Baton Rouge, LA 70803-4001, USA
3 Department of Physics, KTH Royal Institute of Technology - 10691 Stockholm, Sweden
4 Department of Physics, School of Science, Huzhou University - Huzhou, Zhejiang 313000, China
Received: 4 September 2020
Accepted: 14 October 2020
It is shown that the isovector np-pair number operator can be realized in the O(5) quasi-spin basis. The computation of the isovector np-pair number is demonstrated for even-even and odd-odd ds-shell nuclei described by the charge-independent mean field plus isovector pairing model restricted within the O(5) seniority-zero subspace, thereby binding energies and low-lying excited states of these ds-shell nuclei are fit, along with estimates for the isovector neutron-proton pairing contributions. For reasonable neutron-proton pairing strengths the isovector np-pairing energy contribution to the total binding energy in odd-odd N = Z nuclei is systematically larger than that in the even-even nuclei. In sum, the results suggest that the isovector np-pairing mode is favored in odd-odd N = Z nuclei; and additionally, a decrease in the double binding-energy difference for odd-odd nuclei is primarily due to the symmetry and Wigner energy contributions to the binding energy.
PACS: 21.60.Fw – Models based on group theory / 21.60.Cs – Shell model
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