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Dijon, A. et al, Gadea, A., & Huyuk, T. (2012). Discovery of a new isomeric state in Ni-68: Evidence for a highly deformed proton intruder state. Phys. Rev. C, 85(3), 031301–5pp.
Abstract: We report on the observation of a new isomeric state in Ni-68. We suggest that the newly observed state at 168(1) keV above the first 2(+) state is a pi(2p-2h) 0(+) state across the major Z = 28 shell gap. Comparison with theoretical calculations indicates a pure proton intruder configuration and the deduced low-lying structure of this key nucleus suggests a possible shape coexistence scenario involving a highly deformed state.
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Al-Dahan, N. et al, Algora, A., Molina, F., & Rubio, B. (2012). Multiple beta(-) decaying states in Re-194: Shape evolution in neutron-rich osmium isotopes. Phys. Rev. C, 85(3), 034301–9pp.
Abstract: beta decays from heavy, neutron-rich nuclei with A similar to 190 have been investigated following their production via the relativistic projectile fragmentation of an E/A = 1 GeV Pb-208 primary beam on a similar to 2.5 g/cm(2) Be-9 target. The reaction products were separated and identified using the GSI FRagment Separator (FRS) and stopped in the RISING active stopper. gamma decays were observed and correlated with these secondary ions on an event-by-event basis such that gamma-ray transitions following from both internal (isomeric) and beta decays were recorded. A number of discrete, beta-delayed gamma-ray transitions associated with beta decays from Re-194 to excited states in Os-194 have been observed, including previously reported decays from the yrast I-pi = (6(+)) state. Three previously unreported gamma-ray transitions with energies 194, 349, and 554 keV are also identified; these transitions are associated with decays from higher spin states in Os-194. The results of these investigations are compared with theoretical predictions from Nilsson multi-quasiparticle (MQP) calculations. Based on lifetime measurements and the observed feeding pattern to states in Os-194, it is concluded that there are three beta(-)-decaying states in Re-194.
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de Angelis, G. et al, & Gadea, A. (2012). Shape isomerism and shape coexistence effects on the Coulomb energy differences in the N = Z nucleus As-66 and neighboring T=1 multiplets. Phys. Rev. C, 85(3), 034320–7pp.
Abstract: Excited states of the N = Z = 33 nucleus As-66 have been populated in a fusion-evaporation reaction and studied using gamma-ray spectroscopic techniques. Special emphasis was put into the search for candidates for the T = 1 states. A new 3(+) isomer has been observed with a lifetime of 1.1(3) ns. This is believed to be the predicted oblate shape isomer. The excited levels are discussed in terms of the shell model and of the complex excited Vampir approaches. Coulomb energy differences are determined from the comparison of the T = 1 states with their analog partners. The unusual behavior of the Coulomb energy differences in the A = 70 mass region is explained through different shape components (oblate and prolate) within the members of the same isospin multiplets. This breaking of the isospin symmetry is attributed to the correlations induced by the Coulomb interaction.
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Liu, B. C., & Xie, J. J. (2012). The K- p -> eta Lambda reaction in an effective Lagrangian model. Phys. Rev. C, 85(3), 038201–4pp.
Abstract: We report on a theoretical study of the K- p -> eta Lambda reaction near threshold by using an effective Lagrangian approach. The role of s-channel Lambda(1670), t-channel K*, and u-channel proton pole diagrams are considered. We show that the total cross section data are well reproduced. However, only including the s-wave Lambda(1670) state and the background contribution from t and u channels is not enough to describe the bowl structures in the angular distribution of the K- p -> eta Lambda reaction, which indicates that there should be higher partial waves contributing to this reaction in some energy region. Indeed, if we considered the contributions from a D-03 resonance, we could describe the bowl structures; however, a rather small width (similar to 2 MeV) of this resonance would be needed.
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n_TOF Collaboration(Calviani, M. et al), Giubrone, G., & Tain, J. L. (2012). Neutron-induced fission cross section of Cm-245: New results from data taken at the time-of-flight facility n_TOF. Phys. Rev. C, 85(3), 034616–10pp.
Abstract: The neutron-induced fission cross section of Cm-245 was measured at n_TOF in a wide energy range and with high resolution. The energy dependence, measured in a single measurement from 30 meV to 1 MeV neutron energy, has been determined with 5% accuracy relative to the U-235(n,f) cross section. In order to reduce the uncertainty on the absolute value, the data have been normalized at thermal energy to recent measurements performed at ILL and BR1. In the energy range of overlap, the results are in fair agreement with some previous measurements and confirm, on average, the evaluated cross section in the ENDF/B-VII.0 database, although sizable differences are observed for some important resonances below 20 eV. A similar behavior is observed relative to JENDL/AC-2008, a reactor-oriented database for actinides. The new results contribute to the overall improvement of the databases needed for the design of advanced reactor systems and may lead to refinements of fission models for the actinides.
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Montanari, D. et al, & Gadea, A. (2012). Gamma spectroscopy of calcium nuclei around doubly magic Ca-48 using heavy-ion transfer reactions. Phys. Rev. C, 85(4), 044301–21pp.
Abstract: The. decays of neutron-rich Ca isotopes around Ca-48 were measured at Legnaro National Laboratory with the PRISMA-CLARA setup, using the heavy-ion transfer reactions Ca-48 on Ni-64 and Ca-48 on Pb-208 at approximate to 6 MeV/A. The work shows the feasibility to perform full in-beam gamma spectroscopy with heavy-ion transfer reactions (in terms of angular distributions, polarizations, and lifetimes analysis), providing a method that can be further exploited in the future with heavy targets and radioactive beams. For the one-neutron transfer channels, Ca-49 and Ca-47, shell-model and particle-vibration coupling calculations are used to understand the nature of the states. In particular, in both nuclei evidence is found for particle-vibration coupled states based on the 3(-) phonon of Ca-48. In the two-neutron transfer channels, Ca-46 and Ca-50, the experimental data are in global agreement with predictions based on full fp shell-model calculations.
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Sohler, D. et al, & Algora, A. (2012). High-spin structure of Pd-104. Phys. Rev. C, 85(4), 044303–13pp.
Abstract: The high-spin structure of the nucleus Pd-104 was studied through the Zr-96(C-13,5n) reaction at incident energies of 51 and 58MeV, using the Euroball IV gamma-ray spectrometer in conjunction with the DIAMANT charged-particle array. Several new medium- and high-spin bands were revealed. The already known positive-parity yrast and the negative-parity cascades were extended up to E-x similar to 13, similar to 11, and similar to 9 MeV with I-pi = (26(+)), I-pi = (23(-)), and (20(-)), respectively. The deduced band structures were compared with Woods-Saxon total Routhian surface (TRS) calculations. In addition, non-yrast low-lying positive-parity bands were identified, which were assigned to soft gamma-vibrational excitations.
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Haider, H., Ruiz Simo, I., & Sajjad Athar, M. (2012). nu((nu)over-bar)-Pb-208 deep-inelastic scattering. Phys. Rev. C, 85(5), 055201–11pp.
Abstract: Nuclear-medium effects on the weak structure functions F-2(x, Q(2)) and F-3(x, Q(2)) in charged-current neutrino and antineutrino induced deep-inelastic reactions in Pb-208 have been studied. The calculations have been performed in a theoretical model using relativistic nuclear spectral functions which incorporate Fermi motion, binding, and nucleon correlations. We have also included the pion and rho meson cloud contributions calculated from a microscopic model for meson-nucleus self-energies. Using these structure functions, differential scattering cross sections have been obtained and compared with the CERN Hybrid Oscillation Research Apparatus (CHORUS) data. The results for the ratios 2F(i)(Pb)/208F(i)(D), 4F(i)(Pb)/208F(i)(He), 12F(i)(Pb)/208F(i)(C), 16F(i)(Pb)/208F(i)(O), and 56F(i)(Pb)/208F(i)(Fe) (i = 2, 3) have also been obtained and compared with some of the phenomenological fits.
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n_TOF Collaboration(Guerrero, C. et al), Domingo-Pardo, C., & Tain, J. L. (2012). Measurement and resonance analysis of the Np-237 neutron capture cross section. Phys. Rev. C, 85(4), 044616–15pp.
Abstract: The neutron capture cross section of Np-237 was measured between 0.7 and 500 eV at the CERN n_TOF facility using the 4 pi BaF2 Total Absorption Calorimeter. The experimental capture yield was extracted minimizing all the systematic uncertainties and was analyzed together with the most reliable transmission data available using the SAMMY code. The result is a complete set of individual as well as average resonance parameters [D-0 = 0.56(2) eV, <Gamma(gamma)> = 40.9(18) meV, 10(4)S(0) = 0.98(6), R' = 9.8(6) fm]. The capture cross section obtained in this work is in overall agreement with the evaluations and the data of Weston and Todd [Nucl. Sci. Eng. 79, 184 (1981)], thus showing sizable differences with respect to previous data from Scherbakov et al. [J. Nucl. Sci. Technol. 42, 135 (2005)] and large discrepancies with data Kobayashi et al. [J. Nucl. Sci. Technol. 39, 111 (2002)]. The results indicate that a new evaluation combining the present capture data with reliable transmission data would allow reaching an accuracy better than 4%, in line with the uncertainty requirements of the nuclear data community for the design and operation of current and future nuclear devices.
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n_TOF Collaboration(Massimi, C. et al), Domingo-Pardo, C., & Tain, J. L. (2012). Resonance neutron-capture cross sections of stable magnesium isotopes and their astrophysical implications. Phys. Rev. C, 85(4), 044615–15pp.
Abstract: We have measured the neutron capture cross sections of the stable magnesium isotopes Mg-24,Mg-25,Mg-26 in the energy range of interest to the s process using the neutron time-of-flight facility n_TOF at CERN. Capture events from a natural metal sample and from samples enriched in Mg-25 and Mg-26 were recorded using the total energy method based on (C6H6)-H-2 detectors. Neutron resonance parameters were extracted by a simultaneous resonance shape analysis of the present capture data and existing transmission data on a natural isotopic sample. Maxwellian-averaged capture cross sections for the three isotopes were calculated up to thermal energies of 100 keV and their impact on s-process analyses was investigated. At 30 keV the new values of the stellar cross section for Mg-24, Mg-25, and Mg-26 are 3.8 +/- 0.2 mb, 4.1 +/- 0.6 mb, and 0.14 +/- 0.01 mb, respectively.
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