γ-ray spectroscopy ofTe132through β decay of aSb132

Abstract

γ -ray spectroscopy of 132 Te, obtained from β − decay of a 132 Sb radioactive beam at the Holifield Radioactive Ion Beam Facility, was performed using the Clarion array. A significantly revised γ -decay scheme for 132 Te was obtained including a number of new, likely 2 + , states below 2.5 MeV and the removal of a 3 − state at 2280 keV. A simple shell-model interpretation is discussed for the low-lying levels.

Particle-core Couplings Close to Neutron-rich Doubly-magic Nuclei

“…Based on shell model calculations, it has been found that all known states up to 10 + are given mostly by neutron excitations, while the newly found transitions depopulate states most likely arising from neutron and proton excitations. [18,19]. New transitions found in this work are given as gray/pink, thick arrows originating from states with tentative spin assignments.…”

“…This gave the possibility to investigate nuclei close to the 132 Sn doubly-magic core, in which microsecond isomers were identified in previous works. This is the case of 132 Te, 133 Sb and 130 Sn [4,[18][19][20][21]. The analysis was based on double and triple γ-coincidence histograms constructed either requiring correlations among γ-rays prompt with fission events (an event with γ-ray fold larger than 4 recorded within 200 ns was considered a fission event) or requesting correlations between prompt and delayed transitions (a transition was considered delayed if it occured within 200 ns and 20 µs after the prompt event and was not associated with multiplicity higher than 3).…”

“…Transitions known from neutroninduced fission and β-decay of 132 Sb, reported in Refs. [18,19], are given in black, while EXILL results from the analysis of the fission data with the 241 Pu target are indicated in gray/pink, thick arrows. The latter were obtained by making use of prompt-delayed γ-γ coincidences, with gates set on known delayed transition depopulating the isomeric states.…”

One-phonon isovector 2+1,MSstate in the neutron rich nucleus132Te

“…132 Te is one of the first radioactive neutron-rich nuclei in which the B(E2; 2 + 1 → 0 + 1 ) value was measured in projectile Coulomb excitation reactions of a RIB [1]. The excited states of 132 Te have been identified in a γ -γ measurement following the β − decay of 132 Sb [26]. The second excited state at 1665.3 keV discovered in the latter study decays predominantly to the 2 + 1 state by a 690.9 keV transition and to the ground state by a very weak 1665.3 keV transition [I γ (691 keV)/I γ (1665 keV) = 100(52)].…”

“…From this observation, together with the coincidence conditions and the background subtraction procedure, it is clear that the 691-keV γ line represents the decay of a low-lying Coulomb-excited state of 132 Te. Indeed, a γ ray with this energy is known [26] in the decay scheme of 132 Te. It represents the (2 + 2 ) → 2 + 1 transition.…”