Evolution of proton single-particle states in neutron-rich Sb isotopes beyond N=82

Abstract

The β decay of the semimagic Sn isotopes 136,137,138 Sn has been studied at the Radioactive Isotope Beam Factory at the RIKEN Nishina Center. The first experimental information on excited states was obtained for 137 Sb while, in the case of 136 Sb, the established excitation scheme could be extended by ten previously unidentified levels. In the decay of the most-neutron-rich isotope 138 Sn, two γ rays were observed for the first time. The new experimental results, in combination with state-of-the-art shell-model calculations, provide the first information with respect to the evolution of the 0g 7/2 and 1d 5/2 proton single-particle states with increasing neutron number beyond N = 84.

Nuclear structure of Te isotopes beyond neutron magic number N=82

“…A similar difference between the two calculations is found for the unknown yrast 3/2 − state (see Fig. 9) and for the yrast 5/2 + and 3/2 + states of 137 Sb [31].…”

“…An alternative method to detect multiple β-decaying states is to compare the β feeding to the 2 + 1 and 4 + 1 states in two different β-decaying cascades, namely 138 Sb → 138 Te and 138 Sn → 138 Sb → 138 Te. However, this method can unfortunately not be applied in the present case due to the low statistics obtained for the 138 Sn decay in the present experiment [31]. As shown in Fig.…”

“…The only relevant Gamow-Teller (GT) decay in this region is the ν0h 9/2 → π 0h 11/2 transition, which is hindered by the small occupancy of the ν0h 9/2 orbital in the ground states of these nuclei. Recently, the population of a state at 2641 keV in 136 Sb in the β decay of 136 Sn with log f t = 5.2(2) was proposed to correspond to such an allowed 0 + → (1 + ) transition [31]. In that case, 1 + states with the proper configuration were identified in the shell-model calculations 0.64/0.86 MeV too high in energy.…”

First observation of the π0h11/2⊗ν0h9/2 partner orbital configuration in the odd-odd Moon1, Gargano2, Naïdja3 et al. 2022Phys. Rev. CSelf Cite

“…The experiment was performed at the Radioactive Isotope Beam Factory (RIBF) operated by the RIKEN Nishina Center for Accelerator-Based Science and the Center for Nuclear Study of the University of Tokyo. Secondary beams were produced by the in-flight fission of a primary 238 U beam at 345 MeV per nucleon, impinging on a 9 Be target [12]. The produced rare-isotope beams were selected in the first stage of the BigRIPS spectrometer, and identified by the Bρ-E -TOF (time-of-flight) method in the second stage of the BigRIPS and the Zero-Degree Spectrometer [13].…”

“…Furthermore, the proton shell evolution in odd-mass (A) Sb isotopes was investigated in detail and experimental data suggested a possible inversion of the π 0g 7/2 and π 1d 5/2 orbitals with increasing neutron number [9,10]. It is also worth noting that some states in odd-A Sb and Te isotopes were interpreted within the seniority scheme, by considering, respectively, seniority-2 and seniority-3 configurations in the ν1 f 7/2 orbit [8,9].…”