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Szilner, S. et al, & Gadea, A. (2011). Interplay between single-particle and collective excitations in argon isotopes populated by transfer reactions. Phys. Rev. C, 84(1), 014325–7pp.
Abstract: New gamma transitions have been identified in argon isotopes in (40)Ar + (208)Pb multiple transfer reactions by exploiting, in a fragment-gamma measurement, the new generation of magnetic spectrometers based on trajectory reconstruction coupled to large gamma arrays. The coupling of single-particle degrees of freedom to nuclear vibration quanta was discussed. The interpretation of the newly observed states within a particle-phonon coupling picture was used to consistently follow, via their excitation energies, the evolution of collectivity in odd Ar isotopes. The proposed level schemes are supported by the results of sd-pf shell-model calculations, which have been also employed to evaluate the strength functions of the populated states.
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Morales, A. I. et al, Agramunt, J., Algora, A., Gadea, A., Molina, F., & Rubio, B. (2011). Synthesis of N=127 isotones through (p,n) charge-exchange reactions induced by relativistic (208)Pb projectiles. Phys. Rev. C, 84(1), 011601–5pp.
Abstract: The production cross sections of four N = 127 isotones ((207)Hg, (206)Au, (205)Pt, and (204)Ir) have been measured using (p,n) charge-exchange reactions, induced in collisions of a (208)Pb primary beam at 1 A GeV with a Be target. These data allow one to investigate the use of a reaction mechanism to extend the limits of the chart of nuclides toward the important r-process nuclei in the region of the third peak of elemental abundance distribution.
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Corradi, L., Szilner, S., Pollarolo, G., Colo, G., Mason, P., Farnea, E., et al. (2011). Single and pair neutron transfers at sub-barrier energies. Phys. Rev. C, 84(3), 034603–10pp.
Abstract: Multinucleon transfer cross sections in the (96)Zr+(40)Ca system have been measured, in inverse kinematics, at bombarding energies ranging from the Coulomb barrier to similar to 25% below. Targetlike recoils have been identified in A, Z and velocity with the large solid angle magnetic spectrometer PRISMA. The experimental data for one- and two-neutron transfer channels have been compared with semiclassical microscopic calculations. For the two-neutron transfer channels the relevance of the transitions to the ground state and to the 0(+) excited states of (42)Ca are discussed by employing, for the reaction mechanism, the successive approximation. It is found that the transition to the 0(+) state at similar to 6 MeV, whose wave function is dominated by the two neutrons in the 2p(3/2) shell, is much larger than the ground state one. The comparison with the inclusive data reveals that transitions to states with high multipolarity and non-natural parity are important. This suggests that more complex two-particle correlations have to be incorporated in the treatment of the transfer process.
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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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Montanari, D. et al, & Gadea, A. (2011). Elastic, inelastic, and one-nucleon transfer processes in (48)Ca+(64)Ni. Phys. Rev. C, 84(5), 9pp.
Abstract: Elastic, inelastic, and one-nucleon transfer channels in the (48)Ca+(64)Ni reaction have been measured at approximate to 6 MeV/nucleon with the PRISMA-CLARA setup, at Legnaro National Laboratory, consisting of the coupling of a large solid angle magnetic spectrometer with a germanium array. By trajectory reconstruction the reaction products have been fully identified in mass, nuclear charge, and kinetic energy, while coincident gamma spectra of binary partners have been constructed after Doppler correction. Absolute differential cross sections have been extracted for the inelastic excitation and one-nucleon transfer, also for specific excited states. The data are in good agreement with semiclassical calculations and distorted wave Born approximation predictions. The work outlines an experimental method which can become valuable to extract structural information from heavy-ion reaction studies.
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Krolas, W. et al, & Gadea, A. (2011). Coupling of the proton-hole and neutron-particle states in the neutron-rich (48)K isotope. Phys. Rev. C, 84(6), 064301–8pp.
Abstract: Excited states in the Z = 19, N = 29 neutron-rich (48)K isotope have been studied using deep-inelastic transfer reactions with a thick target at Gammasphere and with a thin target at the PRISMA-CLARA spectrometer. The lowest excited states were located; they involve a proton hole in the s(1/2) or d(3/2) orbital coupled to a p(3/2) neutron. A new 7.1(5)-ns, 5(+) isomer, the analog of the 7/2 isomer in (47)K, was identified. Based on the observed gamma-decay pattern of the isomer a revised spin-parity assignment of 1(-) is proposed for the ground state of (48)K.
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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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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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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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Recchia, F. et al, & Gadea, A. (2012). Spectroscopy of odd-mass cobalt isotopes toward the N=40 subshell closure and shell-model description of spherical and deformed states. Phys. Rev. C, 85(6), 064305–10pp.
Abstract: The neutron-rich cobalt isotopes up to A = 67 have been studied through multinucleon transfer reactions by bombarding a U-238 target with a 460-MeV Zn-70 beam. Unambiguous identification of prompt gamma rays belonging to each nucleus has been achieved using coincidence relationships with the ions detected in a high-acceptance magnetic spectrometer. The new data are discussed in terms of the systematics of the cobalt isotopes and interpreted with large-scale shell-model calculations in the fpgd model space. In particular, very different shapes can be described in Co-67, at the edge of the island of inversion at N = 40, where a low-lying highly deformed band coexists with a spherical structure.
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