Few nucleon systems at the exotic doubly magic region 132Sn

Abstract: The low-energy structure of 133Sn, 133Sb and 133Te has been studied. The levels of 133Sn were populated in the β-delayed neutron decay of 134In at the ISOLDE PS-Booster (PSB) mass-separator facility at CERN. The single-neutron states p3/2, h9/2 and f5/2 in 133Sn were identified at 853.7, 1560.9 and 2004.9 -keV, respectively. The β-decays of 133Sn→133Sb and 133Sb→ 133Te were investigated at the fission-product mass separator OSIRIS at Studsvik. As a result, the level schemes of 133Sb and 133Te have been extended considerably. In 133Sb, the single-proton d3/2 level was found at 2439.5 keV with a γ-ray branching giving B(M1; d3/2→d5/2) / B(E2; d3/2→g7/2) = 0.037(3) where the transitions are in Weisskopf units (W.u.). For the h11/2 state at 2791.3 keV, a half-life of 11.4(4.5) ps was measured, giving B(M2; hll/2→g7/2) = 0.55(22) W.u. and B(E3; h11/2→d5/2 = 22(13) W.u.. A comparison with the only other known doubly magic region at medium mass (208Pb) shows that the single-proton transition strengths in 133Sb and 209Bi are remarkably similar. Levels at higher energies in 133Sb are interpreted as core-coupled states with the g7/2 odd proton coupled to the excited states of the 132Sn core. A part of this work was intended to obtain data pertaining to the development of methods for the production of new exotic nuclides. The fusion reaction probabilities with 181Ta were measured for the projectiles 32S and 38S, produced by fragmentation of a primery beam of 40Ar in a Be target. The observed cross sections indicate a lowering of the fusion barrier heights for neutron rich projectiles, of sufficient magnitude that the production rates of heavy nuclei may be enhanced by factors in the range 10-1000.