A diagonalization scheme for the shell model mean-field plus isovector pairing Hamiltonian in the O(5) tensor product basis of the quasi-spin SU${}_{\mathrm{\Lambda }}$(2) ⊗ SU${}_I$(2) chain is proposed. The advantage of the diagonalization scheme lies in the fact that not only can the isospin-conserved, charge-independent isovector pairing interaction be analyzed, but also the isospin symmetry breaking cases. More importantly, the number operator of the np-pairs can be realized in this neutron and proton quasi-spin basis, with which the np-pair occupation number and its fluctuation at the J = 0${}^{+}$ ground state of the model can be evaluated. As examples of the application, binding energies and low-lying J = $0^{+}$ excited states of the even–even and odd–odd N∼Z $ds$-shell nuclei are fit in the model with the charge-independent approximation, from which the neutron–proton pairing contribution to the binding energy in the $ds$-shell nuclei is estimated. It is observed that the decrease in the double binding-energy difference for the odd–odd nuclei is mainly due to the symmetry energy and Wigner energy contribution to the binding energy that alter the pairing staggering patten. The np-pair amplitudes in the np-pair stripping or picking-up process of these N = Z nuclei are also calculated.

中文翻译：

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等向量配对模型中的 np-Pair 相关性

准自旋SU的O(5)张量积基中壳模型平均场加等向量配对哈密顿量的对角化方案${}_{\mathrm{\Lambda }}$(2) ⊗ SU${}_{\mathrm{一世}}$(2)链提出。对角化方案的优势在于，不仅可以分析同位旋守恒、电荷无关的等位向量配对相互作用，还可以分析同位旋对称性破坏情况。更重要的是，np-pairs的数算符可以在这个中子和质子准自旋基中实现，其中np-pair占据数及其在J = 0时的波动${}^{+}$可以评估模型的基态。作为应用的例子，结合能和低位 J =$0^{+}$ 偶-偶和奇-奇 N∼Z 的激发态 $d秒$-壳核与电荷无关的近似拟合在模型中，从中子 - 质子配对对结合能的贡献 $d秒$-shell 核被估计。据观察，奇偶核双结合能差的减小主要是由于对称能和维格纳能对结合能的贡献改变了配对交错模式。还计算了这些 N = Z 核的 np-pair 剥离或拾取过程中的 np-pair 振幅。