Double-Magic Nature of 132Sn and 208Pb through Lifetime and Cross-Section Measurements.

Single-neutron states in 132Sn and 208Pb , which are analogous to single-electron states outside of closed atomic shells in alkali metals, were populated by the (9Be, 8Be) one-neutron transfer reaction in inverse kinematics using particleγ coincidence spectroscopy. In addition, the s 1/2 single-neutron hole-state candidate in 131 Sn was populated by (9Be, 10Be). Doubly closed-shell 132Sn (radioactive) and 208Pb (stable) beams were used at sub-Coulomb barrier energies of 3 MeV per nucleon. Level energies, γ-ray transitions, absolute cross sections, spectroscopic factors, asymptotic normalization coefficients, and excited-state lifetimes are reported and compared with shell-model expectations. The results include a new transition and precise level energy for the 3p1/2 candidate in 133 Sn, new absolute cross sections for the 1 h9/2 candidate in 133Sn and 3s1/2 candidate in 131Sn, and new lifetimes for excited states in 133Sn and 209Pb. This is the first report on excited-state lifetimes of 133Sn, which allow for a unique test of the nuclear shell model and 132Sn double-shell closure. [ABSTRACT FROM AUTHOR]