
Theoretical Nuclear Physics
The theoretical nuclear physics group deals with two interconnected topics: Nuclear Structure and Nuclear Reactions. The structure is investigated by means of nuclear models (shell, collective, algebraic) that idealize the nucleus as a few- or many-body system, with the aim of predicting measurable properties such as energy levels, radii, momenta and electromagnetic transitions, decay rates, etc. The fundamental interest lies in probing symmetries or introducing correlations to understand new aspects of the strong interaction. Through reactions the nucleus is probed, obtaining spectroscopic information on the energy levels. For example, electromagnetic processes allow to study fundamental aspects and to establish the role of continuum states. Reactions are also interesting in themselves, due to the complex mechanisms that are established for example in a reaction between heavy ions.
Staff
Full Professors: Silvia Lenzi
Associate Professors: Lorenzo Fortunato
External collaborators
Paolo Lotti (INFN)
Research activities
Clustering and molecular aspects of light nuclei
The emergence of nucleon clusters (especially alpha clusters) in the structure of the lightest nuclei with mass numbers between 6 and 20 is a phenomenon whose fundamental characteristics are not yet fully understood. There is ample evidence for molecular cluster states, for which theories similar to those of quantum chemistry can be applied, but corrected by typical aspects of nuclear structure. Furthermore, cluster properties also emerge in the phenomenology of nuclear reactions involving light nuclei with interesting implications for fields such as nuclear fusion and stellar astrophysics. We propose and study algebraic and molecular models, studying rotational and vibrational bands and applying them to the study of crucial reactions.
Contacts: Lorenzo Fortunato
Evolution of shells in neutron- or proton-rich nuclei and breaking of isospin symmetry
Microscopic approaches based on effective interaction are studied in the shell model for nuclei ranging from the valley of stability to radioactive nuclei to drip-lines. In particular, isotope chains extending into the neutron-rich or proton-rich regions of the Segré chart are studied comparatively, highlighting the change of magic numbers and the consequences. Isospin symmetry breaking in nuclear interaction is investigated by analyzing energy differences between analogous states in isobaric multiplets (TED and MED). We study the evolution of shells through fundamental properties such as radii and momenta and electromagnetic transitions, comparing our predictions with experimental observations.
Contacts: Silvia Lenzi
Collective Geometric Model and Quantum Phase Transitions
We study the geometric model Collective Quadrupole (Bohr-Mottelson) and the Interacting Boson Model (Arima-Iachello) through various solution techniques: numerical, algebraic (Lie alg.), differential eq., using potential energy surfaces that allow the study of nuclear shapes (spherical, axial prolate/oblate, triaxial) and of the shape phase transitions between them. The mathematical analysis of the transition properties (cross-over, 1st order, 2nd order, etc.) between the various exact limits of the theory allows to extract information on the collective spectra, on the electromagnetic transitions in medium-heavy mass nuclei and compare them with the experiment.
Contacts: Lorenzo Fortunato