Speaker
Angela Gargano
(INFN- Sezione di Napoli)
Description
The shell structure of the atomic nucleus is one of the main ingredients underlying our understanding of nuclear systems. During the last two decades we have recognized that the shell structure may significantly change when going far from valley of stability. Various aspects of the underlying nuclear forces have been shown to be relevant in determining its evolution as a function of the neutron-to-proton ratio, but we are still far from a comprehensive assessment of the phenomenon. Within this context, the region around the doubly-magic nucleus 132Sn is of particular importance. It is, in fact, the only region around a heavy, neutron-rich doubly-closed shell nucleus far-off stability experimentally accessible today. Experimental information on 132Sn neighborings is also relevant for testing the main ingredients of the nuclear-shell model, to be then used to predict the properties of still unknown nuclei towards the neutron drip line.
Besides the nuclear structure aspect, nuclei around 132Sn play a key role in the dynamics of the rapid neutron-capture process of nucleosynthesis, the so-called r-process, since some of these nuclei are acting as bottleneck for the reaction flow. The unknown evolution of the shell structure in this region is one of the main sources of nuclear physics uncertainty in r -process calculations.
This has provided significant motivation for experiments on 132Sn neighborings as well as for a number of theoretical calculations.
In this contribution, we shall focus on nuclei with a few valence particles and/or holes close to 132Sn by comparing the available experimental data with the results of realistic shell-model calculations. The full N=50–82 major shell for neutrons and the Z=28–50 shell for protons are considered and the two-body matrix elements of the effective interaction derived from the CD-Bonn potential [1], whose high momentum repulsive components are smoothed out using the Vlow-k approach [2], by way of many-body perturbation theory [2]. The single-particle energies are taken, whenever possible, from experiment.
The comparison between theory and experiment will be performed for nuclei situated in all four quadrants around 132Sn, including those in the south quadrants for which data are very scanty.
This approach has the major merit that no adjustable parameter is required, which makes it particularly appropriate to investigate regions, where the lack of experimental information precludes, for the moment, the development of empirical interactions. On the other hand, it has proved to lead to an accurate description of nuclear structure in various mass regions and also around 132Sn (see, for instance [4]), where, however, attention has been focused in particular on nuclei with Z>50.
[1] R. Machleidt, Phys. Rev. C 63, 024001(R) (2001)
[2] L. Coraggio, A. Covello, A. Gargano, N. Itaco, and T. T. S. Kuo,
Prog. Part. Nucl. Phys. 62, 135 (2009)
[3] L. Coraggio, A. Covello, A. Gargano, and N. Itaco, Phys. Rev. C 88,
041304(R), and references therein
Primary author
Angela Gargano
(INFN- Sezione di Napoli)
