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Perez-Cerdan, A. B., Rubio, B., Gelletly, W., Algora, A., Agramunt, J., Burkard, K., et al. (2011). beta decay of (78)Sr. Phys. Rev. C, 84(5), 054311–15pp.
Abstract: The gamma rays and conversion electrons emitted in the beta decay of (78)Sr to levels in (78)Rb have been studied using Ge detectors and a mini-orange spectrometer. A reliable level scheme based on the results of these experiments has been established. The properties of the levels in (78)Rb have been compared with calculations based on deformed Hartree-Fock with Skyrme interactions and pairing correlations in the BCS approximation. This has allowed an interpretation of the nature of the observed sets of levels in the odd-odd nucleus (78)Rb.
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Kaya, L. et al, & Gadea, A. (2018). Millisecond 23/2(+) isomers in the N=79 isotones Xe-133 and Ba-135. Phys. Rev. C, 98(5), 054312–16pp.
Abstract: Detailed information on isomeric states in A approximate to 135 nuclei is exploited to shell-model calculations in the region northwest of doubly magic nucleus Sn-132. The N = 79 isotones Xe-133 and Ba-135 are studied after multinucleon transfer in the Xe-136 + Pb-208 reaction employing the high-resolution Advanced GAmma Array (AGATA) coupled to the magnetic spectrometer PRISMA at the Laboratori Nazionali di Legnaro, Italy and in a pulsed-beam experiment at the FN tandem accelerator of the University of Cologne Germany utilizing a Be-9 + Te-130 fusion-evaporation reaction at a beam energy of 40 MeV. Isomeric states are identified via delayed gamma-ray spectroscopy. Hitherto tentative excitation energy spin and parity assignments of the 2017-keV J(pi) = 23/2(+) isomer in Xe-133 are confirmed and a half-life of T-1/2 = 8.64(13) ms is measured. The 2388-keV state in Ba-135. is identified as a J(pi) = 23/2(+) isomer with a half-life of 1.06(4) ms. The new results show a smooth onset of isomeric J(pi) = 23/2(+) states along the N = 79 isotones and close a gap in the high-spin systematics towards the recently investigated J(pi) = 23/2(+) isomer in Nd-139. The resulting systematics of M2 reduced transition probabilities is discussed within the of the nuclear shell model. Latest large-scale shell-model calculations employing the SN100PN, GCN50:82, SN100-KTH and a realistic effective interaction reproduce the experimental findings generally well and give insight into the structure of the isomers.
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Mukha, I. et al. (2010). Spectroscopy of proton-unbound nuclei by tracking their decay products in-flight: One- and two-proton decays of F-15, Ne-16, and Na-19. Phys. Rev. C, 82(5), 054315–14pp.
Abstract: A powerful method of investigating proton-unbound nuclear states by tracking their decay products in flight is discussed in detail. To verify the method, four known levels in F-15, Ne-16, and Na-19 were investigated by measuring the angular correlations between protons and the respective heavy-ion fragments stemming from the precursor decays in flight. The parent nuclei of interest were produced in nuclear reactions of one-neutron removal from Ne-17 and Mg-20 projectiles at energies of 410-450 A MeV. The trajectories of the respective decay products, O-14 + p + p and Ne-18 + p + p, were measured by applying a tracking technique with microstrip detectors. These data were used to reconstruct the angular correlations of the fragments, which provided information on energies and widths of the parent states. In addition for reproducing properties of known states, evidence for hitherto unknown excited states in F-15 and Ne-16 was found. This tracking technique has an advantage in studies of exotic nuclei beyond the proton drip line measuring the resonance energies and widths with a high precision although by using low-intensity beams and very thick targets.
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Fernandez, A. et al, Gadea, A., Perez-Vidal, R. M., Jurado, M., & Domingo-Pardo, C. (2021). Reinterpretation of excited states in Po-212: Shell-model multiplets rather than alpha-cluster states. Phys. Rev. C, 104(5), 054316–19pp.
Abstract: A gamma-ray spectroscopic study of Po-212 was performed at the Grand Accelerateur National d'Ions Lourds, using the inverse kinematics alpha-transfer reaction C-12(Pb-208, Po-212) Be-8 and the AGATA spectrometer. A careful analysis based on gamma gamma coincidence relations allowed us to establish 14 new excited states in the energy range between 1.9 and 3.3 MeV. None of these states, however, can be considered as candidates for the levels with spins and parities of 1(-) and 2(-) and excitation energies below 2.1 MeV, which have been predicted by recent alpha-cluster model calculations. A systematic comparison of the experimentally established excitation scheme of Po-212 with shell-model calculations was performed. This comparison suggests that the six states with excitation energies (spins and parities) of 1744 (4(-)), 1751 (8(-)), 1787 (6(-)), 1946 (4(-)), 1986 (8(-)), and 2016 (6(-)) keV, which previously were interpreted as alpha-cluster states, may in fact be of positive parity and belong to low-lying shell-model multiplets. This reinterpretation of the structure of Po-212 is supported by experimental information with respect to the linear polarization of gamma rays, which suggests a magnetic character of the 432-keV gamma ray decaying from the state at an excitation energy of 1787 keV to the 6(1)(+) yrast state, and exclusive reaction cross sections.
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AGATA Collaboration(Goldkuhle, A. et al), Perez-Vidal, R. M., Domingo-Pardo, C., & Gadea, A. (2019). Lifetime measurements in Ti-52,Ti-54 to study shell evolution toward N=32. Phys. Rev. C, 100(5), 054317–12pp.
Abstract: Lifetimes of the excited states in the neutron-rich Ti-52,Ti-54 nuclei, produced in a multinucleon-transfer reaction, were measured by employing the Cologne plunger device and the recoil-distance Doppler-shift method. The experiment was performed at the Grand Accelerateur National d'Ions Lourds facility by using the Advanced Gamma Tracking Array for the gamma-ray detection, coupled to the large-acceptance variable mode spectrometer for an event-by-event particle identification. A comparison between the transition probabilities obtained from the measured lifetimes of the 2(1)(+) to 8(1)(+) yrast states in Ti-52,Ti-54 and that from the shell-model calculations based on the well-established GXPF1A, GXPF1B, and KB3G fp shell interactions support the N = 32 subshell closure. The B(E2) values for Ti-52 determined in this work are in disagreement with the known data, but are consistent with the predictions of the shell-model calculations and reduce the previously observed pronounced staggering across the even-even titanium isotopes.
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AGATA Collaboration(Soderstrom, P. A. et al), & Gadea, A. (2012). High-spin structure in K-40. Phys. Rev. C, 86(5), 054320–9pp.
Abstract: High-spin states of K-40 have been populated in the fusion-evaporation reaction C-12(Si-30,np)K-40 and studied by means of gamma-ray spectroscopy techniques using one triple-cluster detector of the Advanced Gamma Tracking Array at the Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro. Several states with excitation energy up to 8 MeV and spin up to 10(-) have been discovered. These states are discussed in terms of J = 3 and T = 0 neutron-proton hole pairs. Shell-model calculations in a large model space have shown good agreement with the experimental data for most of the energy levels. The evolution of the structure of this nucleus is here studied as a function of excitation energy and angular momentum.
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Szilner, S. et al, & Gadea, A. (2013). Structure of chlorine isotopes populated by heavy ion transfer reactions. Phys. Rev. C, 87(5), 054322–12pp.
Abstract: Neutron-rich chlorine isotopes were populated in the Ar-40 + Pb-208 multiple transfer reaction via the -1p channels in a fragment-gamma coincident measurement employing the Prisma-Clara setup. New gamma transitions have been identified and, together with already available data, level schemes have been revised and compared with the results of large-scale sd-pf shell-model calculations. The evolution of the energy splitting between the s(1/2) and d(3/2) orbitals and the increased mixing of different proton configurations in the populated Cl isotopic chain have been deduced by inspecting the shell-model wave functions.
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Diel, F., Fujita, Y., Fujita, H., Cappuzzello, F., Ganioglu, E., Grewe, E. W., et al. (2019). High-resolution study of the Gamow-Teller (GT_) strength in the Zn-64(He-3, t) Ga-64 reaction. Phys. Rev. C, 99(5), 054322–10pp.
Abstract: Gamow-Teller (GT) transitions starting from the T-z = +2 nucleus Zn-64 to the T-z = +1 nucleus Ga-64 were studied in a (p, n)-type (He-3,t) charge-exchange reaction at a beam energy of 140 MeV/nucleon and scattering angles close to 0 degrees. Here, T-z is the z component of the isospin T. The experiment was conducted at the Research Center for Nuclear Physics (RCNP) in Osaka, Japan. An energy resolution of approximate to 34 keV was achieved by applying beam matching techniques to the Grand Raiden magnetic spectrometer system. With our good resolution, we could observe GT strength fragmented in many states up to an excitation energy of approximate to 11 MeV. By performing angular distribution analysis, we could identify states in Ga-64 excited by GT transitions. The reduced GT transition strengths [B(GT)values] were calculated assuming the proportionality between the cross sections and the B(GT)values. Shell-model calculations using the GXPF1J interaction reproduced the B(GT)strength distribution throughout the spectrum. States with isospin T = 3 were identified by comparing the Zn-64(He-3,t)Ga-64 spectrum with a Zn-64(d, He-2)Cu-64 spectrum. Relative excitation energies of the corresponding structures are in good agreement, supporting the robustness of isospin symmetry in the mass number A = 64 nuclei.
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Moschner, K. et al, & Algora, A. (2016). Relativistic Coulomb excitation of Kr-88. Phys. Rev. C, 94(5), 054323–5pp.
Abstract: To investigate the systematics of mixed-symmetry states in N = 52 isotones, a relativistic Coulomb excitation experiment was performed during the PreSPEC campaign at the GSI Helmholtzzentrum fur Schwerionenforschung to determine E2 transition strengths to 2(+) states of the radioactive nucleus Kr-88. Absolute transition rates could be measured towards the first and third 2+ states. For the latter a mixed-symmetry character is suggested on the basis of the indication for a strong M1 transition to the fully symmetric 2(1)(+) state, extending the knowledge of the N = 52 isotones below Z = 40. A comparison with the proton-neutron interacting boson model and shell-model predictions is made and supports the assignment.
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Taprogge, J. et al, Gadea, A., & Montaner-Piza, A. (2015). beta decay of Cd-129 and excited states in In-129. Phys. Rev. C, 91(5), 054324–11pp.
Abstract: The beta decay of Cd-129, produced in the relativistic fission of a U-238 beam, was experimentally studied at the RIBF facility at the RIKEN Nishina Center. From the gamma radiation emitted after the beta decays, a level scheme of In-129 was established comprising 31 excited states and 69 gamma-ray transitions. The experimentally determined level energies are compared to state-of-the-art shell-model calculations. The half-lives of the two beta-decaying states in Cd-129 were deduced and the beta feeding to excited states in In-129 were analyzed. It is found that, as in most cases in the Z < 50, N <= 82 region, both decays are dominated by the nu 0g(7/2) -> pi 0g(9/2) Gamow-Teller transition, although the contribution of first-forbidden transitions cannot be neglected.
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