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We report on a shell-model study of Sn isotopes beyond N 82 employing a realistic effective interaction derived from the CD-Bonn nucleon-nucleon potential renormalized through use of the Vlow-k approach. At present, the most exotic Sn isotope for which some experimental information exists is 134Sn with an N/Z ratio of 1.68. It is the aim of our study to compare the results of our calculations with the available experimental data and to make predictions for the neighboring heavier isotopes which may be within reach of the next generation of radioactive ion beam facilities. The very good agreement between theory and experiment obtained for 134Sn gives confidence in the predictive power of our realistic shell-model calculations.

This paper presents a short overview of the shell-model approach with realistic effective interactions to the study of exotic nuclei. We first give a sketch of the current state of the art of the theoretical framework of this approach, focusing on the main ingredients and most relevant recent advances. Then, we present some selected results for neutron-rich nuclei in various mass regions, namely oxygen isotopes, N 40 isotones, and nuclei around 132Sn, to show the merit as well as the limits of these calculations.

A major requirement for a nuclear model is, not only to reproduce and describe accurately the available experimental data, but also to provide reliable predictions for physical quantities not yet measured. Over the past two decades, we have performed various realistic shell-model calculations for nuclei in different mass regions, which have all yielded results in good agreement with the available experimental data. In this paper we present some selected results illustrating their predictive power.

We investigate the pairing properties of an effective shell-model interaction defined within a model space outside 132Sn 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 134Sn and 134Te. 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.

We report on a shell-model study of nuclei with four valence nucleons in the 132Sn and 208Pb regions. This aims at investigating to what extent the striking similarity existing between the low-energy properties of 134Sb and 210Bi persists when adding a pair of identical particles. We employ realistic low-momentum effective interactions derived from the CD-Bonn nucleon-nucleon potential through use of the Vlow-k approach. The calculated results are in very good agreement with the available experimental data and emphasize the persistence of a close resemblance between the spectroscopy of the two regions when moving away from the one proton-one neutron systems.

We study the neutron-rich calcium isotopes performing shell-model calculations with a realistic effective interaction. This is derived from the CD-Bonn nucleon-nucleon potential renormalized by way of the Vlow–k approach, considering 48Ca as an inert core and including the neutron 0g9/2 orbital. We compare our results with experiment and with the results of a previous study where 40Ca was assumed as a closed core and the standard 1p0f model space was employed. The calculated spectroscopic properties are in both cases in very good agreement with the available experimental data and enable a discussion on the role of the g9/2 single-particle state in the heavy-mass Ca isotopes.

The advent of nucleon-nucleon potentials derived from chiral perturbation theory, as well as the so-called Vlow-k approach to the renormalization of the strong short-range repulsion contained in the potentials, have brought renewed interest in realistic shell-model calculations. Here we focus on calculations where a fully microscopic approach is adopted. No phenomenological input is needed in these calculations, because single-particle energies, matrix elements of the two-body interaction, and matrix elements of the electromagnetic multipole operators are derived theoretically. This has been done within the framework of the time-dependent degenerate linked-diagram perturbation theory. We present results for some nuclei in different mass regions. These evidence the ability of realistic effective hamiltonians to provide an accurate description of nuclear structure properties.

This volume gives a comprehensive overview of the latest research activity undertaken in the field of theoretical nuclear physics in Italy. Several topics of current interest are included: from nuclear matter and nuclear structure to nuclear astrophysics and quark-gluon plasma.

The decay of a T1/2 19(3) μs isomeric state from 125Cd has been observed using γ-ray spectroscopy at the Lohengrin mass spectrometer of the Institut Laue-Langevin, Grenoble. Two coincident γ rays were observed to be emitted from the decay of this isomeric state, contradicting recently published data on this nucleus. Realistic shell-model calculations have been performed to interpret the decay scheme, allowing a spin and parity of 19/2+ to be assigned to the isomeric state. All configurations contributing to this isomeric state have amplitudes less than 7 %. Experimental data have recently been published on the decays of μs isomeric states in 127,128,130Cd. Realistic shell-model calculations for these nuclei are presented which reproduce the known experimental decay schemes reasonably well.

This volume gives a comprehensive overview of the latest research activity undertaken in the field of theoretical nuclear physics in Italy. Several topics of current interest are included: from nuclear matter and nuclear structure to nuclear astrophysics and quark-gluon plasma.