Exotic nuclear spectroscopy: towards the doubly-magic Sn-100

Modern nuclear spectroscopy boosts the study of the nuclear matter towards extreme conditions: large excitation energies, high spins, and new nuclear species with unusual ratio between the numbers of neutrons and protons. One of the 'exotic' nuclear regions, practically not studied until now, is the upper part of the N=Z line, from about N∼Z∼36 to Sn-100, probably the heaviest bound nucleus with N=Z. These nuclei lie close to the proton-drip line. Due to their special composition, it is expected that their study will reveal some phenomena which are less encountered in the nuclei studied till now. In particular, of outstanding interest is the fact that these are the only nuclei which may provide information on the properties of the neutron-proton pairing forces. In spite of its large interest, this nuclear region is exceedingly difficult to reach with the present techniques. The lecture follows the latest results and efforts in the study of the heaviest nuclei with N∼Z. The described experiments, of gamma-ray spectroscopy with heavy-ion beams, have been carried out at the Legnaro accelerator with the Germanium array GASP, and its ancillary detectors for neutrons, charged particles, and reaction products. One presents original results concerning the level schemes of the heaviest N=Z nuclei reached to date, Mo-84 and Ru-88, as well as of their neighbours with N=Z+1, Mo-85, Ru-89, and Rh-91. One emphasizes different interesting structure systematics, as well as effects which may be related to the neutron-proton pairing interaction. Possible future extensions of these experimental investigations are briefly mentioned. (author)