Nucleon-nucleon correlations probed in sub-barrier transfer reactions and the nuclear Josephson effect

In recent years a series of near- and sub-barrier transfer experiments have been carried out at LNL, with reaction products detected in inverse kinematics and at forward angles with the large solid angle magnetic spectrometer PRISMA. Nucleon-nucleon correlation properties have been studied by measuring transfer cross sections far below the Coulomb barrier, making excitation functions down to very low energies and corresponding to very large distances of closest approach where the nuclear absorption is small. Such kind of studies are of general interest since one probes the tails of the density distributions. One subtle case is the possible manifestation of a nuclear Josephson effect. Predictions have been made of a specific gamma strength function associated with the dipole oscillations generated by the, mainly successive, two neutron transfer process. The coupling of PRISMA to the AGATA gamma array, recently installed at LNL, offered a unique opportunity to study such an effect. In a very recent experiment we directly tested for the first time the possible manifestation of Cooper pair oscillations, observed to date only in condensed matter physics.