Double-Magic Nature ofSn132andPb208

Abstract

Single-neutron states in (133)Sn and (209)Pb, which are analogous to single-electron states outside of closed atomic shells in alkali metals, were populated by the ((9)Be, (8)Be) one-neutron transfer reaction in inverse kinematics using particle-γ coincidence spectroscopy. In addition, the s(1/2) single-neutron hole-state candidate in (131)Sn was populated by ((9)Be, (10)Be). Doubly closed-shell (132)Sn (radioactive) and (208)Pb (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 3p(1/2) candidate in (133)Sn, new absolute cross sections for the 1h(9/2) candidate in (133)Sn and 3s(1/2) candidate in (131)Sn, and new lifetimes for excited states in (133)Sn and (209)Pb. This is the first report on excited-state lifetimes of (133)Sn, which allow for a unique test of the nuclear shell model and (132)Sn double-shell closure.

Recent Direct Reaction Experimental Studies with Radioactive Tin Beams

“…This is the most reasonable explanation for how these states were populated in this reaction [13]. Similar states were not observed in experiments using the ( 9 Be, 8 Be γ) reaction on beams of 132 Sn [9] and 134 Te [10], which do not have an isomeric component. [7,8].…”

“…The total energy of each CsI signal was measured, as was the slow component, referred to as the tail, as shown in figure 2. Separate groups for α particles, 9 Be ions, and scattered 130 Sn beam particles can be clearly resolved. may strike the same crystal giving a very clean tag of the reaction, the 2α group marked in figure 2.…”

“…Sn studied with the ( 9 Be, 8 Be γ) reaction A series of detailed transfer reaction studies of nuclei around 132 Sn [7][8][9][10] and N = 50 above Z = 28 [11,12] were performed at the HRIBF. Inverse kinematics (d, p) experiments on beams of 130 Sn and 132 Sn resulted in the population of excited states of 131 Sn from across the N = 82 shell closure with properties similar to those seen at low excitations in 133 Sn.…”

“…Inverse kinematics (d, p) experiments on beams of 130 Sn and 132 Sn resulted in the population of excited states of 131 Sn from across the N = 82 shell closure with properties similar to those seen at low excitations in 133 Sn. These states were further studied using the ( 9 Be, 8 Be γ) reaction on beams of 130 Sn [13] and 132 Sn [9]. The focus here is on the 130 Sn beam results.…”

Early Signal of Emerging Nuclear Collectivity in Neutron-Rich Sb129

“…In seeking to understand the emergence of nuclear collectivity, it is essential to study E2 transition strengths, which may begin to show collective features before the patterns associated with deformed collective excitations (e.g., anharmonic vibrations and rotations) emerge in the energy levels.The region around double-magic 132 Sn is now accessible through experiments on radioactive beams. This provides an excellent opportunity to investigate the emergence of nuclear collectivity from the underlying singleparticle motion because 132 Sn is a robust doubly magic core [3][4][5][6][7]. In particular, 132 Sn does not have deformed multi-particle, multi-hole states at low-excitation energy (like 16 O and 40 Ca) that can mix with the lowest-lying states and complicate the interpretation of shell-model calculations.…”