Physics of Neutron-Rich Nuclei

One of the main avenues addressed by radioactive ion beams is the evolution of nuclear structure as a function of neutron-to-proton asymmetry.

  

Figure 1: Diagram illustrating the range of isoscalar densities and neutron excess, (N-Z)/A, important in various areas of nuclear physics and astrophysics (based on Ref. [5]).

Figure 1 shows various domains of nuclear matter, important in the context of the RNB program. The range of neutron excess, (N-Z)/A, in finite nuclei is from about -0.2 (proton drip line) to 0.5 (neutron drip line). Of course, by using radioactive beams (and radioactive targets), one will be able to explore new regions of Fig. 1. In particular, the new-generation RNB facilities, such as the Rare Isotope Accelerator, will provide a unique capability for accessing the very asymmetric nuclear matter and for compressing neutron-rich matter approaching density regimes important for supernova and neutron star physics.

From a theoretical point of view, exotic neutron-rich nuclei far from stability are of particular interest. They offer a unique test of those components of effective interactions that depend on the isospin degrees of freedom. In many respects, weakly bound nuclei are much more difficult to treat theoretically than well-bound systems [4]. For weakly bound nuclei, the Fermi energy lies very close to zero, and the particle continuum must be taken into account explicitly.