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Modamio, V., Jungclaus, A., Algora, A., Bazzacco, D., Escrig, D., Fraile, L. M., et al. (2010). New high-spin isomer and quasiparticle-vibration coupling in Ir-187. Phys. Rev. C, 81(5), 054304–13pp.
Abstract: The high-spin structure of the Z = 77 nucleus Ir-187 has been studied using the fusion-evaporation reaction W-186(Li-7, (6)n) at a beam energy of 59 MeV. The excitation scheme of this nucleus has been extended by more than 110 new states, including extensions of all previously established rotational bands. The band crossing region of the h(9/2) negative-parity yrast band has been revised and new intrinsic high-K states have been identified. In particular, a 29/2(-) isomeric state [T-1/2 = 1.8(5)mu s] at an excitation energy of 2487 keV has been observed for the first time, and on top of it, a rich level scheme reaching up to spin (59/2(-)) and excitation energies around 7 MeV has been established.
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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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Stanja, J. et al, Agramunt, J., & Algora, A. (2013). Mass spectrometry and decay spectroscopy of isomers across the Z=82 shell closure. Phys. Rev. C, 88(5), 054304–7pp.
Abstract: Recent results from a measurement campaign studying the isomerism in neutron-deficient Tl isotopes are presented. The measurements make use of a nuclear spectroscopy setup coupled to the high-resolution Penningtrap mass spectrometer ISOLTRAP at CERN's radioactive ion-beam facility ISOLDE. The mass values of Tl-190,Tl-194 are improved and a mass-spin-state assignment is carried out. An additional mass measurement of the grandparent nuclide At-198 allows the deduction of the spin-state ordering in Tl-190. As a result, the excitation energies of the isomers in both Tl isotopes are determined for the first time to Eex(Tl-194) = 260(15) keV and E-ex(Tl-190) = 89(12) keV. Furthermore, this allows anchoring of the ground-state and isomer masses of Bi-194, Fr-202, and Ac-206, which are linked by two independent a-decay chains.
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Wendt, A. et al, & Algora, A. (2014). Isospin symmetry in the sd shell: Transition strengths in the neutron-deficient sd shell nucleus Ar-33. Phys. Rev. C, 90(5), 054301–7pp.
Abstract: Reduced transition strengths of the deexciting transitions from the first two excited states in Ar-33 were measured in a relativistic Coulomb excitation experiment at the GSI Helmholtz center. The radioactive ion beam was produced by fragmentation of a primary Ar-36 beam on a Be-9 target followed by the selection of the reaction product of interest via the GSI Fragment Separator. The (33A)r beam hit a secondary Au-197 target with an energy of approximately 145 MeV/nucleon. An array of high-purity germanium cluster detectors and large-volume BaF2 scintillator detectors were employed for gamma-ray spectroscopy at the secondary target position. The Lund-York-Cologne Calorimeter was used to track the outgoing ions and to identify the nuclear reaction channels. For the two lowest energy excited states of Ar-33 the reduced transition strengths have been determined. With these first results the T-z = -3/2 nucleus Ar-33 is now, together with Na-21 (T-z = -1/2), the only neutron-deficient odd-A sd shell nucleus in which experimental transition strengths are available. The experimental values are compared to results of shell-model calculations which describe simultaneously mirror-energy differences and transition-strength values of mirror pairs in the sd shell in a consistent way.
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Briz, J. A., Nacher, E., Borge, M. J. G., Algora, A., Rubio, B., Dessagne, P., et al. (2015). Shape study of the N = Z nucleus Kr-72 via beta decay. Phys. Rev. C, 92(5), 054326–10pp.
Abstract: The beta decay of the N = Z nucleus Kr-72 has been studied with the total absorption spectroscopy technique at ISOLDE (CERN). A total B(GT) = 0.79(4)g(A)(2)/4 pi has been found up to an excitation energy of 2.7 MeV. The B(GT) distribution obtained is compared with predictions from state-of-the-art theoretical calculations to learn about the ground state deformation of Kr-72. Although a dominant oblate deformation is suggested by direct comparison with quasiparticle random phase approximation (QRPA) calculations, beyond-mean-field and shell-model calculations favor a large oblate-prolate mixing in the ground state.
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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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Gottardo, A. et al, Gadea, A., & Algora, A. (2019). New spectroscopic information on Tl-211,Tl-213: A changing structure beyond the N=126 shell closure. Phys. Rev. C, 99(5), 054326–7pp.
Abstract: The neutron-rich isotopes Tl-211,Tl-213, beyond the N = 126 shell closure, have been studied for the first time in isomer gamma-ray decay, exploiting the fragmentation of a primary uranium beam at the Fragment Separator-Rare Isotopes Investigation at GSI setup. The observed isomeric states in Tl-211,Tl-213 show a deviation from the seniority-like scheme of Tl-209. The possible interpretation of the data is discussed on the basis of energy-level systematics and shell-model calculations.
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IDS Collaboration(Andel, B. et al), Algora, A., & Nacher, E. (2021). New beta-decaying state in Bi-214. Phys. Rev. C, 104(5), 054301–13pp.
Abstract: A new beta-decaying state in Bi-214 has been identified at the ISOLDE Decay Station at the CERN-ISOLDE facility. A preferred I-pi = (8(-)) assignment was suggested for this state based on the beta-decay feeding pattern to levels in Po-214 and shell-model calculations. The half-life of the I-pi = (8) state was deduced to be T-1/2 = 9.39(10) min. The deexcitation of the levels populated in Po-214 by the beta decay of this state was investigated via gamma-gamma coincidences and a number of new levels and transitions was identified. Shell-model calculations for excited states in Bi-214 and Po-214 were performed using two different effective interactions: the H208 and the modified Kuo-Herling particle interaction. Both calculations agree on the interpretation of the new beta-decaying state as an I-pi = 8 – isomer and allow for tentative assignment of shell-model states to several high-spin states in Po-214.
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HISPEC-DESPEC Collaboration(Polettini, M. et al), Algora, A., Morales, A. I., & Orrigo, S. E. A. (2022). Decay studies in the A similar to 225 Po-Fr region from the DESPEC campaign at GSI in 2021. Nuovo Cim. C, 45(5), 125–4pp.
Abstract: The HISPEC-DESPEC collaboration aims at investigating the struc-ture of exotic nuclei formed in fragmentation reactions with decay spectroscopymeasurements, as part of the FAIR Phase-0 campaign at GSI. This paper reportson first results of an experiment performed in spring 2021, with a focus on beta-decaystudies in the Po-Fr nuclei in the 220 < A <230 island of octupole deformationexploiting the DESPEC setup. Ion-beta correlations and fast-timing techniques arebeing employed, giving an insight into this difficult-to-reach region.
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Guess, C. J. et al, Algora, A., Estevez, E., Molina, F., & Rubio, B. (2011). The Nd-150(He-3,t) and Sm-150(t,He-3) reactions with applications to beta beta decay of Nd-150. Phys. Rev. C, 83(6), 064318–17pp.
Abstract: The Nd-150(3He,t) reaction at 140 MeV/u and Sm-150(t,He-3) reaction at 115 MeV/u were measured, populating excited states in Pm-150. The transitions studied populate intermediate states of importance for the (neutrinoless) beta beta decay of Nd-150 to Sm-150. Monopole and dipole contributions to the measured excitation-energy spectra were extracted by using multipole decomposition analyses. The experimental results were compared with theoretical calculations obtained within the framework of the quasiparticle random-phase approximation, which is one of the main methods employed for estimating the half-life of the neutrinoless beta beta decay (0 nu beta beta) of Nd-150. The present results thus provide useful information on the neutrino responses for evaluating the 0 nu beta beta and 2 nu beta beta matrix elements. The 2 nu beta beta matrix element calculated from the Gamow-Teller transitions through the lowest 1(+) state in the intermediate nucleus is maximally about half that deduced from the half-life measured in 2 nu beta beta direct counting experiments, and at least several transitions through 1+ intermediate states in Pm-150 are required to explain the 2 nu beta beta half-life. Because Gamow-Teller transitions in the Sm-150(t,3He) experiment are strongly Pauli blocked, the extraction of Gamow-Teller strengths was complicated by the excitation of the 2 (h) over bar omega, Lambda L = 0, Delta S = 1 isovector spin-flip giant monopole resonance (IVSGMR). However, the near absence of Gamow-Teller transition strength made it possible to cleanly identify this resonance, and the strength observed is consistent with the full exhaustion of the non-energy-weighted sum rule for the IVSGMR.
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