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Structure of the neutron-rich N=86 isotope 140Xe, located northeast of a doubly-magic nucleus 132Sn, is investigated by β−γ spectroscopy. Two β-decay isomers in 140I are newly found in the study of two different β decays of 140I which were produced by two reactions (i) direct in-flight fission at a primary target and (ii) β decay of 140Te at an active stopper. Half-lives of the β decays of the ground state, the low-spin isomer, and the high-spin isomer are determined to be 0.38(2), 0.91(5), and 0.47(4) s, respectively. Decay schemes of the β decay of the high-spin isomer and of the mixed β decays of the ground state and the low-spin isomer in 140I to 140Xe are constructed using the information on γ-ray coincidence relation and γ-ray intensity. Nuclear structures of the low-lying states in 140Xe and 140I are discussed by comparing the experimental results to two theoretical calculations based on a large-scale shell model and the deformed Skyrme Hartree-Fock-Bogoliubov plus deformed quasiparticle-random-phase approximation. Possible candidates for (quasi-)γ-band members of 2+ and 4+ states and the octupole collective 1− state are proposed in 140Xe. Increase of quadrupole, triaxial, and octupole collectivities is discussed with the increase of neutron and proton numbers.

The β-decay scheme of 138Te and the level structure of 138I is reported for the first time. The experiment was performed at the Radioactive Isotope Beam Factory of RIKEN, as one of the EUROBALL-RIKEN Cluster Array campaigns. Secondary radioactive ions, including 138Te and 138Sb, were produced by the in-flight fission of a 238U beam with the energy of 345 MeV per nucleon. From the β decay of 138Te, the level scheme of 138I was supplemented with new spin and parity assignments, such as the low-lying negative-parity states and a positive-parity 1+ state. This 1+ state can be interpreted as being associated with the π0h11/2⊗ν0h9/2 partner orbital configuration populated by the Gamow-Teller transition between a neutron in the 0h9/2 orbital and a proton in the 0h11/2 orbital. Details of the structure of 138I are discussed in terms of the proton-neutron interactions and Gamow-Teller transition strength within the theoretical context of shell-model calculations.

The β-decay half-lives of 55 neutron-rich nuclei 134−139Sn, 134−142Sb, 137−144Te, 140−146I, 142−148Xe, 145−151Cs, 148−153Ba, and 151−155La were measured at the Radioactive Isotope Beam Factory employing the projectile fission fragments of 238U. The nuclear level structure, which relates to deformation, has a large effect on the half-lives. The impact of newly measured half-lives on modeling the astrophysical origin of the heavy elements is studied in the context of r process nucleosynthesis. For a wide variety of astrophysical conditions, including those in which fission recycling occurs, the half-lives have an important local impact on the second (A ≈ 130) peak.

11 pags., 10 figs., 3 tabs., We report on new γ-ray spectroscopy results from β decays of In99 and Sn101. 30 new γ rays were observed following the β decay of In99, and inconsistencies in the literature with respect to the γ rays following the β decay of Sn101 were addressed with two confirmed cases and two new transitions. The experimental γ-ray energies, intensities, and coincidence relationships are discussed with shell model calculations, where theoretical β-decay branching ratios from the parent nuclei and γ-ray cascades of excited states from the daughter nuclei were combined to generate hypothetical βγ spectra and βγγ coincidence matrices. The most intense β-delayed γ-ray branches in both Cd99 and In101 were well reproduced with this approach, and several γ rays were assigned to new excited states based on their good agreement with shell model predictions., The authors would like to thank the personnel at the RIKEN Nishina Center for providing the exotic radioactive isotope beam with record intensities. This experiment was performed at RI Beam Factory operated by RIKEN Nishina Center and CNS, University of Tokyo. We acknowledge the EUROBALL Owners Committee for loaning the germanium detectors and the PreSpec Collaboration for the readout electronics of the cluster detectors of EURICA. Support for the WAS3ABi setup was provided by the Rare Isotope Science Project, funded by the Ministry of Education, Science and Technology (MEST) and National Research Foundation (NRF) of Korea, as well as KAKENHI (Grant No. 25247045) of Japan Society for the Promotion of Science (JSPS). This work was supported by the Institute for Basic Science (IBS-R031-D1). The authors acknowledge also the support of the DFG cluster of excellence “Origin and Structure of the Universe,” German BMBF under Contracts No. 05P15PKFNA and No. 05P19PKFNA, and the Spanish Ministerio de Economía y Competitividad via Project No. FPA2017-84756-C4-2-P. Part of the research was funded by the Natural Sciences and Engineering Research Council (NSERC) of Canada and also supported by FJNSP LIA (French-Japanese International Associated Laboratory for Nuclear Structure Problems)

6 pags., 4 figs., A record number of Sn100 nuclei was detected and new isotopic species toward the proton dripline were discovered at the RIKEN Nishina Center. Decay spectroscopy was performed with the high-efficiency detector arrays WAS3ABi and EURICA. Both the half-life and the β-decay end point energy of Sn100 were measured more precisely than the literature values. The value and the uncertainty of the resulting strength for the pure 0+→1+ Gamow-Teller decay was improved to BGT=4.4-0.7+0.9. A discrimination between different model calculations was possible for the first time, and the level scheme of In100 is investigated further., This work was carried out at the RIBF operated by RIKEN Nishina Center, RIKEN and CNS, University of Tokyo. It was supported and financed by the DFG cluster of excellence “Origin and Structure of the Universe,” the German BMBF under Contracts No. 05P12WOFNF and No. 05P15PKFNA, the Hanns-Seidel-Stiftung, and the RIKEN IPA Programme. We wish to acknowledge the EURICA RIBF09 collaboration as well as the support on the WAS3ABi setup from the Rare Isotope Science Project, funded by the Ministry of Education, Science and Technology and National Research Foundation of Korea KAKENHI (Grant No. 25247045). Part of the research was also funded by the Natural Sciences and Engineering Research Council of Canada, supported by FJNSP LIA (French-Japanese International Associated Laboratory for Nuclear Structure Problems) and by the Spanish Ministerio de Economía y Competitividad under Contract No. FPA2017-84756-C4-2-P.

6 pags., 4 figs., tab. -- Rapid Communications, We report on new or more precise half-lives, beta-decay endpoint energies, and beta-delayed proton emission branching ratios of(91) Pd, Cd-95,In-97, and Sn-99. The measured values are consistent with known mirror transitions in lighter T-z = -1/2 nuclei, shell-model calculations, and various mass models. In addition to the beta -decaying (9/2(+)) ground state, circumstantial evidence for a short-lived, proton-emitting isomer with spin (1 /2(-)) was found in(97)In. Based on the experimental data, a semiempirical theory on proton emission, and shell-model calculations, the proton separation energy of the In-97 ground state was determined to be -0.10 +/- 0.19 MeV. The existence of the short-lived, proton-unstable (1 /2(-)) isomer in In-97 establishes Cd-9S as an rp-process waiting point., This experiment was performed at RI Beam Factory operated by RIKEN Nishina Center and CNS, University of Tokyo.We acknowledge the EUROBALL Owners Committee for loaning the germanium detectors and the PreSpec Collaboration for the readout electronics of the cluster detectors of EURICA. Support for theWAS3ABi setup was provided by the Rare Isotope Science Project, funded by the Ministry of Education, Science and Technology (MEST) and National Research Foundation (NRF) of Korea, as well as KAKENHI (Grant No. 25247045) of the Japan Society for the Promotion of Science (JSPS). The authors acknowledge the support of the DFG cluster of excellence “Origin and Structure of the Universe,” German BMBF under Contract No. 05P15PKFNA and the Spanish Ministerio de Economa y Competitividad via Project No. FPA2014-57196-C5-4-P. Part of the research was funded by the Natural Sciences and Engineering Research Council (NSERC) of Canada and also supported by FJ-NSP (French-Japanese International Associated Laboratory for Nuclear Structure Problems).

Several new isotopes, In-96, Cd-94, Ag-92, and Pd-90, have been identified at the RIKEN Nishina Center. The study of proton drip-line nuclei in the vicinity of Sn-100 led to the discovery of new proton emitters Ag-93 and Rh-89 with half-lives in the submicrosecond range. The systematics of the half-lives of odd-Z nuclei with T-z = -1/2 toward Sn-99 shows a stabilizing effect of the Z = 50 shell closure. Production cross sections for nuclei in the vicinity of Sn-100 measured at different energies and target thicknesses were compared to the cross sections calculated by EPAX taking into account contributions of secondary reactions in the primary target.