|
Taprogge, J. et al, Gadea, A., & Montaner-Piza, A. (2014). 1p(3/2) Proton-Hole State in Sn-132 and the Shell Structure Along N=82. Phys. Rev. Lett., 112(13), 132501–6pp.
Abstract: A low-lying state in In-131(82), the one-proton hole nucleus with respect to double magic Sn-132, was observed by its gamma decay to the I-pi 1/2(-) beta-emitting isomer. We identify the new state at an excitation energy of E-x = 1353 keV, which was populated both in the beta decay of Cd-131(83) and after beta-delayed neutron emission from Cd-132(84), as the previously unknown pi p(3/2) single-hole state with respect to the Sn-132 core. Exploiting this crucial new experimental information, shell-model calculations were performed to study the structure of experimentally inaccessible N = 82 isotones below Sn-132. The results evidence a surprising absence of proton subshell closures along the chain of N = 82 isotones. The consequences of this finding for the evolution of the N = 82 shell gap along the r-process path are discussed.
|
|
|
Taprogge, J. et al, Gadea, A., & Montaner-Piza, A. (2014). Identification of a millisecond isomeric state in Cd-129(81) via the detection of internal conversion and Compton electrons. Phys. Lett. B, 738, 223–227.
Abstract: The decay of an isomeric state in the neutron-rich nucleus Cd-129 has been observed via the detection of internal conversion and Compton electrons providing first experimental information on excited states in this nucleus. The isomer was populated in the projectile fission of a U-238 beam at the Radioactive Isotope Beam Factory at RIKEN. From the measured yields of gamma-rays and internal conversion electrons, a multipolarity of E3 was tentatively assigned to the isomeric transition. A half-life of T-1/2 = 3.6(2) ms was determined for the new state which was assigned a spin of (21/2(+)), based on a comparison to shell model calculations performed using state-of-the-art realistic effective interactions.
|
|
|
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.
|
|
|
Taprogge, J. et al, Gadea, A., & Montaner-Piza, A. (2016). Proton-hole and core-excited states in the semi-magic nucleus In-131(82). Eur. Phys. J. A, 52(11), 347–10pp.
Abstract: The decay of the N = 83 nucleus Cd-131 has been studied at the RIBF facility at the RIKEN Nishina Center. The main purpose of the study was to identify the position of the and proton-hole states and the energies of core-excited configurations in the semi-magic nucleus In-131. From the radiation emitted following the decay, a level scheme of In-131 was established and the feeding to each excited state determined. Similarities between the single-particle transitions observed in the decays of the N = 83 isotones In-132 and Cd-131 are discussed. Finally the excitation energies of several core-excited configurations in In-131 are compared to QRPA and shell-model calculations.
|
|
|
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.
|
|
|
Szilner, S. et al, & Gadea, A. (2013). Transfer Reaction Studies with Spectrometers. Acta Phys. Pol. B, 44(3), 417–426.
Abstract: The revival of transfer reaction studies benefited from the construction of the new generation large solid angle spectrometers, coupled to large gamma arrays. The recent results of gamma-particle coincident measurements in Ca-40+Zr-96 and Ar-40+Pb-208 reactions demonstrate a strong interplay between single-particle and collective degrees of freedom that is pertinent to the reaction dynamics. The development of collectivity has been followed in odd Ar isotopes populated in the Ar-40+Pb-208 reaction through the excitation of the 11/2(-) states, understood as the coupling of single particle degrees of freedom to nuclear vibration quanta. Pair transfer modes is another important degree of freedom which is presently being studied with Prisma in inverse kinematics at energies far below the Coulomb barrier. First results from the Zr-96+Ca-40 reaction elucidate the role played by nucleon-nucleon correlation.
|
|
|
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.
|
|
|
Steinhardt, T., Eberth, J., Skoda, S., Thelen, O., Schwengner, R., Donau, F., et al. (2012). Stabilization of prolate deformation at high spin in Kr-75. Phys. Rev. C, 86(6), 064310–16pp.
Abstract: The neutron-deficient nucleus Kr-75 has been studied in two EUROBALL experiments. The analysis yielded a considerably extended level scheme including two newly observed excited high spin bands. The results are interpreted in the framework of the cranked Nilsson-Strutinsky approach. The calculations compare well to the experimentally established level scheme and predict the nucleus to be mainly prolate or triaxially deformed at high spin. Evidence for an oblate-prolate shape coexistence could not be found at high spin.
|
|
|
Stahl, C. et al., & Gadea, A. (2015). Population of the 2(ms)(+) mixed-symmetry state of Ba-140 with the alpha-transfer reaction. Phys. Rev. C, 92(4), 044324–7pp.
Abstract: Background: Identification of proton-neutron mixed-symmetric one-quadrupole phonon excitations (the 2(ms)(+) states) of atomic nuclei provides information on the isovector part of the residual nucleon-nucleon interaction. It was predicted that the 2(ms)(+) state of particular nuclei close to the U(5) limit of the interacting boson model, in particular Ba-140, should be considerably populated by alpha-transfer reactions [C. E. Alonso et al., Phys. Rev. C 78, 017301 (2008)]. Purpose: We aim at the identification of the 2(ms)(+) mixed-symmetry state (MSS) of radioactive Ba-140 and investigate its population by the alpha-transfer reaction as a suitable tool to selectively populate MSSs and as a potential new signature for its mixed-symmetric character. Method: A gamma-ray spectroscopy experiment was performed in inverse kinematics in order to populate the 2(ms)(+) state of Ba-140 by alpha-transfer from a C-nat target on Xe-136 beam ions. The population of the candidate for the 2(ms)(+) state of Ba-140 was measured relative to the population of the 2(1)(+) state. Results: The candidate for the 2(ms)(+) state of Ba-140 was populated by a transfer three times weaker than predicted. Another 2(+) state that can be ruled out as the MSS was in turn as strongly populated by the a transfer as predicted for the MSS. Conclusions: The relative population of 2(+) states by alpha-transfer cannot serve as a new signature for MSSs, since other 2(+) states are also strongly populated. Nevertheless, the substantial population of the MSS candidate of Ba-140 by alpha transfer qualifies this type of reaction as suitable tool to excite MSSs and study their electromagnetic decay properties.
|
|
|
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.
|
|