Probing the nucleus at  Nuclear Structure under Extreme  Spectroscopy of exotic nuclei

The Nuclear Response to Temperature and Angular Momentum

Over the next five years or so we expect a dramatic improvement in our knowledge of nuclear properties as a function of temperature and angular momentum. In terms of the thermal response the emphasis is on how the elementary modes of excitations are modified by the thermal environment. In this connection the transition from order to chaos, which is expected to occur at rather low temperatures, is of special interest. There will be further emphasis on multiple excitations of giant resonance modes starting with double and then triple excitation. The detail of how the excitation energy affects the coupling of the doorway and compound nuclear states for this basically cold excitation are of vital importance for our understanding of the effective interaction on the nuclear medium. When the giant dipole vibration is thermally excited on very elongated shapes, we expect that one of the components will be shifted to low energy and will strongly affect the E1 transitions in the decay cascades. The focus of experiments on states with high angular momentum will be the observation of new types of exotic nuclear shape such as the hyperdeformed and triaxially superdeformed shapes. The experimental platform for such studies is provided by the new generation of $\gamma$-ray arrays together with their ancillary devices. Open questions such as the existence of ``chiral-twin bands'' and the very elongated shapes predicted in some light nuclei, the so-called alpha-chain states, should be answered. Increased sensitivity and energy resolution will allow us to pin down the symmetries revealed by regularities in rotational band spacings and the corresponding matrix elements. Progress here will require new theoretical insights. Understanding the tunnelling processes involved in the decay of nuclei with exotic shapes will require detailed measurements of the gamma-ray strength function.