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 ²⁰⁶Pb + ¹¹⁸Sn has been measured using particle- 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 -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 -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 ¹²⁰Sn and ¹¹⁶Sn, while the 2n-transition remains in the ground state for the recoiling ^20XPb-nuclei. Large enhancements up to EF 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.Received: 6 November 2002, Revised: 25 March 2003, Published online: 23 March 2004PACS: 24.10.Eq Coupled-channel and distorted-wave models - 25.70.Hi Transfer reactions