Abstract
We investigate the pairing properties of an effective shell-model interaction defined within a model space outside 132 Sn and derived by means of perturbation theory from the CD-Bonn free nucleon-nucleon potential. It turns out that the neutron pairing component of the effective interaction is significantly weaker than the proton one, which accounts for the large pairing gap difference observed in the two-valence identical particle nuclei 134 Sn and 134 Te. The role of the contribution arising from one particle-one hole excitations in determining the pairing force is discussed and its microscopic structure is also analyzed in terms of the multipole decomposition.
Highlights
From the very beginning of nuclear structure studies, pairing has proved to be a main key for understanding many features of nuclei as the odd-even staggering in binding energies, the gap in the excitation spectrum of even-even systems, and the compressed spectrum in odd systems
It turns out that the neutron pairing component of the effective interaction is significantly weaker than the proton one, which accounts for the large pairing gap difference observed in the two-valence identical particle nuclei 134Sn and 134Te
As concerns the effects of the nuclear medium, several works have pointed out that a relevant contribution to the pairing force arises from the exchange of vibrations between nucleon pairs moving in time reversal states close to the Fermi surface [5, 6]
Summary
From the very beginning of nuclear structure studies, pairing has proved to be a main key for understanding many features of nuclei as the odd-even staggering in binding energies, the gap in the excitation spectrum of even-even systems, and the compressed spectrum in odd systems. As concerns the effects of the nuclear medium, several works have pointed out that a relevant contribution to the pairing force arises from the exchange of vibrations between nucleon pairs moving in time reversal states close to the Fermi surface [5, 6]. In all these works, phenomenological or semi-phenomenological approaches have been used. EPJ Web of Conferences ment with experiment for several other nuclei around 132Sn [15,16,17,18,19] On these grounds, one should expect that our effective interaction possesses good pairing properties. A summary of our conclusions is given in the last Section
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