Pairing effects in nucleon transfer reactions in the system144Sm+88Sr at 4.7 MeV/u

Proton and neutron transfer populating low-lying states have been studied in the system¹⁴⁴Sm+⁸⁸Sr at an energy below the Coulomb barrier. The experimental cross sections for the single proton transfer are well reproduced by DWBA-calculations using spectroscopic information from light ion reactions. The two-proton transfer appears enhanced relative to the uncorrelated sequential transfer of single protons. The same holds for the transfer of proton pairs, the enhancement is kept for the second pair. This is interpreted as a supercurrent between two superfluid nuclear proton-pair wave functions: more mass and charge is transported per time unit in pairs than by single nucleons. Neutron transfer is observed with large cross sections and is found to contribute to the energy loss observed in the transfer reactions. For mixed proton-neutron transfers the sequential nature of the transfer reactions is established in a similar way as for the two-proton and two-neutron transfer; in the latter case no enhancement is observed.