Gombas, J., DeYoung, P. A., Spyrou, A., Dombos, A. C., Algora, A., Baumann, T., et al. (2021). beta-decay feeding intensity distributions for Nb-103,Nb-104m. Phys. Rev. C, 103(3), 035803–8pp.
Abstract: The beta decays of Nb-103,Nb-104m were studied with the Summing NaI(Tl) (SuN) detector at the National Superconducting Cyclotron Laboratory. The beta-decay feeding intensity distribution I-beta(E) for each isotope was extracted by measuring gamma rays in coincidence with an emitted electron. The I-beta(E) was extracted via the total absorption spectroscopy technique. The I-beta(E) for each nucleus was compared to predictions made by the quasiparticle random-phase approximation (QRPA) model which is commonly used to calculate beta-decay properties for astrophysical applications. The main goal was to provide experimental data for neutron-rich nuclei, relevant to the astrophysical r process. In addition, the extracted beta-decay feeding intensity distributions can lead to a better understanding of nuclear structure in a region of rapid structure changes around A = 100. Finally, experimental data for Nb-104m are also of interest to antineutrino studies of nuclear reactors.
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Rice, S. et al, Algora, A., Tain, J. L., Valencia, E., Agramunt, J., Rubio, B., et al. (2017). Total absorption spectroscopy study of the beta decay of Br-86 and Rb-91. Phys. Rev. C, 96(1), 014320–10pp.
Abstract: The beta decays of Br-86 and Rb-91 have been studied using the total absorption spectroscopy technique. The radioactive nuclei were produced at the Ion Guide Isotope Separator On-Line facility in Jyvaskyla and further purified using the JYFLTRAP. Br-86 and Rb-91 are considered to be major contributors to the decay heat in reactors. In addition, Rb-91 was used as a normalization point in direct measurements of mean gamma energies released in the beta decay of fission products by Rudstam et al. assuming that this decaywas well known from high-resolution measurements. Our results show that both decays were suffering from the Pandemonium effect and that the results of Rudstam et al. should be renormalized. The relative impact of the studied decays in the prediction of the decay heat and antineutrino spectrum from reactors has been evaluated.
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Estevez, E. et al, Algora, A., Rubio, B., Bernabeu, J., Nacher, E., Tain, J. L., et al. (2011). beta-decay study of (150)Er, (152)Yb, and (156)Yb: Candidates for a monoenergetic neutrino beam facility. Phys. Rev. C, 84(3), 034304–6pp.
Abstract: The beta decays of (150)Er, (152)Yb, and (156)Yb nuclei are investigated using the total absorption spectroscopy technique. These nuclei can be considered possible candidates for forming the beam of a monoenergetic neutrino beam facility based on the electron capture (EC) decay of radioactive nuclei. Our measurements confirm that for the cases studied the EC decay proceeds mainly to a single state in the daughter nucleus.
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Dombos, A. C. et al, & Algora, A. (2021). Total absorption spectroscopy of the beta decay of Zr-101,102 and Tc-109. Phys. Rev. C, 103(2), 025810–20pp.
Abstract: The beta decay of Zr-101,Zr-102 and Tc-109 was studied using the technique of total absorption spectroscopy. The experiment was performed at the National Superconducting Cyclotron Laboratory using the Summing NaI(Tl) (SuN) detector in the first-ever application of total absorption spectroscopy with a fast beam produced via projectile fragmentation. The beta-decay feeding intensity and Gamow-Teller transition strength distributions were extracted for these three decays. The extracted distributions were compared to three different quasiparticle random-phase approximation (QRPA) models based on different mean-field potentials. A comparison with calculations from one of the QRPA models was performed to learn about the ground-state shape of the parent nucleus. For Zr-101 and Zr-102, calculations assuming a pure shape configuration (oblate or prolate) were not able to reproduce the extracted distributions. These results may indicate that some type of mixture between oblate and prolate shapes is necessary to reproduce the extracted distributions. For Tc-109, a comparison of the extracted distributions with QRPA calculations suggests a dominant oblate configuration. The other two QRPA models are commonly used to provide beta-decay properties in r-process network calculations. This work shows the importance of making comparisons between the experimental and theoretical beta-decay distributions, rather than just half-lives and beta-delayed neutron emission probabilities, as close to the r-process path as possible.
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Jungclaus, A. et al, & Montaner-Piza, A. (2020). Evolution of proton single-particle states in neutron-rich Sb isotopes beyond N=82. Phys. Rev. C, 102(3), 034324–11pp.
Abstract: The beta decay of the semimagic Sn isotopes Sn-136,Sn-137,Sn-138 has been studied at the Radioactive Isotope Beam Factory at the RIKEN Nishina Center. The first experimental information on excited states was obtained for Sb-137 while, in the case of Sb-136, the established excitation scheme could be extended by ten previously unidentified levels. In the decay of the most-neutron-rich isotope Sn-138, two gamma 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 Og(7/2) and 1d(5/2) proton single-particle states with increasing neutron number beyond N = 84.
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Jungclaus, A. et al, Gadea, A., & Montaner-Piza, A. (2016). beta decay of semi-magic Cd-130: Revision and extension of the level scheme of In-130. Phys. Rev. C, 94(2), 024303–8pp.
Abstract: The beta decay of the semi-magic nucleus Cd-130 has been studied at the RIBF facility at the RIKEN Nishina Center. The high statistics of the present experiment allowed for a revision of the established level scheme of In-130 and the observation of additional beta feeding to high- lying core-excited states in In-130. The experimental results are compared to shell-model calculations employing a model space consisting of the full major N = 50-82 neutron and Z = 28-50 proton shells and the NA-14 interaction, and good agreement is found.
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Morales, A. I. et al, Algora, A., Rubio, B., Orrigo, S. E. A., Agramunt, J., Gelletly, W., et al. (2017). Simultaneous investigation of the T=1(J(pi)=0(+)) and T=0(J(pi)=9(+)) beta decays in Br-70. Phys. Rev. C, 95(6), 064327–11pp.
Abstract: The beta decay of the odd-odd nucleus Br-70 has been investigated with the BigRIPS and EURICA setups at the Radioactive Ion Beam Factory (RIBF) of the RIKEN Nishina Center. The T = 0(J(pi) = 9(+)) and T = 1(J(pi) = 0(+)) isomers have both been produced in in-flight fragmentation of Kr-78 with ratios of 41.6(8)% and 58.4(8)%, respectively. A half-life of t(1/2) = 2157(-49)(+53) ms has been measured for the J pi = 9(+) isomer from gamma-ray time decay analysis. Based on this result, we provide a new value of the half-life for the J pi = 0(+) ground state of Br-70, t(1/2) = 78.42 +/- 0.51 ms, which is slightly more precise, and in excellent agreement, with the best measurement reported hitherto in the literature. For this decay, we provide the first estimate of the total branching fraction decaying through the 2(1)(+) state in the daughter nucleus Se-70, R(2(1)(+)) = 1.3 +/- 1.1%. We also report four new low-intensity gamma-ray transitions at 661, 1103, 1561, and 1749 keV following the beta decay of the J pi = 9(+) isomer. Based on their coincidence relationships, we tentatively propose two new excited states at 3945 and 4752 keV in 70Se with most probable spins and parities of J(pi) = (6(+)) and (8(+)), respectively. The observed structure is interpreted with the help of shell-model calculations, which predict a complex interplay between oblate and prolate configurations at low excitation energies.
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IDS Collaboration(Piersa-Silkowska, M. et al), & Nacher, E. (2021). First beta-decay spectroscopy of In-135 and new beta-decay branches of In-134. Phys. Rev. C, 101(4), 044328–19pp.
Abstract: The beta decay of the neutron-rich In-134 and In-135 was investigated experimentally in order to provide new insights into the nuclear structure of the tin isotopes with magic proton number Z = 50 above the N = 82 shell. The beta-delayed gamma-ray spectroscopy measurement was performed at the ISOLDE facility at CERN, where indium isotopes were selectively laser-ionized and on-line mass separated. Three beta-decay branches of In-134 were established, two of which were observed for the first time. Population of neutron-unbound states decaying via gamma rays was identified in the two daughter nuclei of In-134, Sn-134 and Sn-133, at excitation energies exceeding the neutron separation energy by 1 MeV. The beta-delayed one-and two-neutron emission branching ratios of In-134 were determined and compared with theoretical calculations. The beta-delayed one-neutron decay was observed to be dominant beta-decay branch of In-134 even though the Gamow-Teller resonance is located substantially above the two-neutron separation energy of Sn-134. Transitions following the beta decay of In-135 are reported for the first time, including gamma rays tentatively attributed to Sn-135. In total, six new levels were identified in Sn-134 on the basis of the beta gamma gamma coincidences observed in the In-134 and In-135 beta decays. A transition that might be a candidate for deexciting the missing neutron single-particle 13/2(+) state in Sn-133 was observed in both beta decays and its assignment is discussed. Experimental level schemes of Sn-134 and Sn-135 are compared with shell-model predictions. Using the fast timing technique, half-lives of the 2(+), 4(+), and 6(+) levels in Sn-134 were determined. From the lifetime of the 4(+) state measured for the first time, an unexpectedly large B(E2; 4(+) -> 2(+)) transition strength was deduced, which is not reproduced by the shell-model calculations.
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Briz, J. A., Nacher, E., Borge, M. J. G., Algora, A., Rubio, B., Dessagne, P., et al. (2015). Shape study of the N = Z nucleus Kr-72 via beta decay. Phys. Rev. C, 92(5), 054326–10pp.
Abstract: The beta decay of the N = Z nucleus Kr-72 has been studied with the total absorption spectroscopy technique at ISOLDE (CERN). A total B(GT) = 0.79(4)g(A)(2)/4 pi has been found up to an excitation energy of 2.7 MeV. The B(GT) distribution obtained is compared with predictions from state-of-the-art theoretical calculations to learn about the ground state deformation of Kr-72. Although a dominant oblate deformation is suggested by direct comparison with quasiparticle random phase approximation (QRPA) calculations, beyond-mean-field and shell-model calculations favor a large oblate-prolate mixing in the ground state.
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Guadilla, V. et al, Algora, A., Tain, J. L., Agramunt, J., Jordan, M. D., Montaner-Piza, A., et al. (2017). Experimental study of Tc-100 beta decay with total absorption gamma-ray spectroscopy. Phys. Rev. C, 96(1), 014319–10pp.
Abstract: The beta decay of Tc-100 has been studied by using the total absorption gamma-ray spectroscopy technique at the Ion Guide Isotope Separator On-Line facility in Jyvaskyla. In this work the new Decay Total Absorption gamma-ray Spectrometer in coincidence with a cylindrical plastic beta detector has been employed. The beta intensity to the ground state obtained from the analysis is in good agreement with previous high-resolution measurements. However, differences in the feeding to the first-excited state as well as weak feeding to a new level at high excitation energy have been deduced from this experiment. Theoretical calculations performed in the quasiparticle random-phase approximation framework are also reported. Comparison of these calculations with our measurement serves as a benchmark for calculations of the double beta decay of Mo-100.
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