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Soderstrom, P. A. et al, Algora, A., & Gadea, A. (2010). Spectroscopy of neutron-rich Dy-168,Dy-170: Yrast band evolution close to the NpNn valence maximum. Phys. Rev. C, 81(3), 034310–5pp.
Abstract: The yrast sequence of the neutron-rich dysprosium isotope Dy-168 has been studied using multinucleon transfer reactions following collisions between a 460-MeV Se-82 beam and an Er-170 target. The reaction products were identified using the PRISMA magnetic spectrometer and the gamma rays detected using the CLARA HPGe-detector array. The 2(+) and 4(+) members of the previously measured ground-state rotational band of Dy-168 have been confirmed and the yrast band extended up to 10(+). A tentative candidate for the 4(+) -> 2(+) transition in Dy-170 was also identified. The data on these nuclei and on the lighter even-even dysprosium isotopes are interpreted in terms of total Routhian surface calculations and the evolution of collectivity in the vicinity of the proton-neutron valence product maximum is discussed.
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Caballero-Folch, R. et al, Agramunt, J., Tain, J. L., Algora, A., Domingo-Pardo, C., Guadilla, V., et al. (2018). First determination of beta-delayed multiple neutron emission beyond A=100 through direct neutron measurement: The P-2n value of Sb-136. Phys. Rev. C, 98(3), 034310–10pp.
Abstract: Background: beta-delayed multiple neutron emission has been observed for some nuclei with A <= 100 being the Rb-100 the heaviest beta 2n emitter measured to date. So far only 25 P-2n values have been determined for the approximate to 300 nuclei that may decay in this way. Accordingly it is of interest to measure P-2n values for the other possible multiple neutron emitters throughout the chart of the nuclides. It is of particular interest to make such a measurement for nuclei with A > 100 to test the predictions of theoretical models and simulation tools for the decays of heavy nuclei in the region of very neutron-rich nuclei. In addition the decay properties of these nuclei are fundamental for the understanding of astrophysical nucleosynthesis processes such as the r-process and safety inputs for nuclear reactors. Purpose: To determine for the first time the two-neutron branching ratio the P-2n value for Sb-136 through a direct neutron measurement and to provide precise P-1n values for Sb-136 and Te-136. Method: A pure beam of each isotope of interest was provided by the JYFLTRAP Penning trap at the Ion Guide Isotope Separator On-Line (IGISOL) facility of the University of Jyvaskyla Finland. The purified ions were implanted into a moving tape at the end of the beam line. The detection setup consisted of a plastic scintillator placed right behind the implantation point after the tape to register the beta decays and the BELEN detector based on neutron counters embedded in a polyethylene matrix. The analysis was based on the study of the beta- and neutron-growth-and-decay curves and the beta-one-neutron and beta-two-neutron time correlations which allowed us the determination of the neutron branching ratios. Results: The P-2n value of Sb-136 was found to be 0.14(3)% and the measured P-1n values for Sb-136 and Te-136 were found to be 32.2(15)% and 1.47(6)% respectively. Conclusions: The measured P-2n value is a factor 44 smaller than predicted by the finite-range droplet model plus the quasiparticle random-phase approximation (FRDM+QRPA) model used for r-process calculations.
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Sarriguren, P., Algora, A., & Pereira, J. (2014). Gamow-Teller response in deformed even and odd neutron-rich Zr and Mo isotopes. Phys. Rev. C, 89(3), 034311–13pp.
Abstract: beta-decay properties of neutron-rich Zr and Mo isotopes are investigated within a microscopic theoretical approach based on the proton-neutron quasiparticle random-phase approximation. The underlying mean field is described self-consistently from deformed Skyrme Hartree-Fock calculations with pairing correlations. Residual separable particle-hole and particle-particle forces are also included in the formalism. The structural evolution in these isotopic chains including both even and odd isotopes is analyzed in terms of the equilibrium deformed shapes. Gamow-Teller strength distributions, beta-decay half-lives, and beta-delayed neutron-emission probabilities are studied, stressing their relevance to describe the path of the nucleosynthesis rapid neutron capture process.
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Vandone, V. et al, Gadea, A., & Huyuk, T. (2013). Global properties of K hindrance probed by the gamma decay of the warm rotating W-174 nucleus. Phys. Rev. C, 88(3), 034312–9pp.
Abstract: The K hindrance to the gamma decay is studied in the warm rotating W-174 nucleus, focusing on the weakening of the selection rules of the K quantum number with increasing excitation energy. W-174 was populated by the fusion reaction of Ti-50 (at 217 MeV) on a Te-128 target, and its gamma decay was detected by the AGATA Demonstrator array coupled to a BaF2 multiplicity filter at Laboratori Nazionali di Legnaro of INFN. A fluctuation analysis of gamma coincidence matrices gives a similar number of low-K and high-K discrete excited bands. The results are compared to simulations of the gamma-decay flow based on a microscopic cranked shell model at finite temperature in which the K mixing is governed by the interplay of Coriolis force with the residual interaction. Agreement between simulations and experiment is obtained only by hindering the E1 decay between low-K and high-K bands by an amount compatible with that determined by spectroscopic studies of K isomers in the same mass region, with a similar trend with excitation energy. The work indicates that K mixing due to temperature effects may play a leading role for the entire body of discrete excited bands, which probes the onset region of K weakening.
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Bello Garrote, F. L. et al, & Morales, A. I. (2020). beta decay of Ni-75 and the systematics of the low-lying level structure of neutron-rich odd-A Cu isotopes. Phys. Rev. C, 102(3), 034314–13pp.
Abstract: Background: Detailed spectroscopy of neutron-rich odd-A Cu isotopes is of great importance for studying the shell evolution in the region of Ni-78. While there is experimental information on excited states in 69-73,77,79CU isotopes, the information concerning Cu-75 is very limited. Purpose: Experimentally observed single-particle, core-coupling, and proton-hole intruder states in Cu-75, will complete the systematics of these states in the chain of isotopes. Method: Excited states in Cu-75 were populated in the beta decay of Ni-75 isotopes. The Ni nuclei were produced by the in-flight fission of U-238 projectiles, and were separated, identified, and implanted in a highly segmented Si detector array for the detection of the beta-decay electrons. The beta-delayed gamma rays were detected in a HPGe cluster array. Monte Carlo shell model calculations were performed using the A3DA interaction built on the pf g(9/2)d(5/2) model space for both neutrons and protons. Results: A level scheme of Cu-75 was built up to approximate to 4 MeV by performing a gamma-gamma coincidence analysis. The excited states below 2 MeV were interpreted based on the systematics of neutron-rich odd-A Cu isotopes and the results of the shell model calculations. Conclusions: The evolution of the single-particle, core-coupling, and proton-hole intruder states in the chain of neutron-rich odd-A Cu isotopes is discussed in the present work, in connection with the newly observed level structure of Cu-75.
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