Selection of cold transfer and enhanced neutron-pair transfer in the 206 Pb + 118 Sn reaction

. The neutron transfer in a very heavy asymmetric nuclear system, in 206 Pb + 118 Sn has been measured using particle- γ coincidence techniques with position-sensitive detectors, 5 EUROBALL-Cluster detectors (EB) and the Heidelberg-Darmstadt NaI-CRYSTAL BALL (CB). The fragments are identified via the known γ -decays of the lowest excited states using the high resolution of EB. Using the unique feature of the set-up with the CB, transfer to well-defined final channels with known quantum numbers is selected using the high-efficiency multiplicity filter of the CB with no second γ -ray, i.e. without feeding. The enhancement in the two-neutron transfer is deduced, for population of the low-lying super-fluid 2 + states in 120 Sn and 116 Sn , while the 2n-transition remains in the ground state for the recoiling 20 X Pb-nuclei. Large enhancements up to EF ≃ 10^3 are observed. This is the first observation of neutron pair-transfer enhancement for a heavy nuclear binary system with superfluid properties with experimentally separated levels.