The structure of $^{80}\mathrm{Ge}$ has been investigated at the ISOLDE facility at CERN. A previous study reported for the first time a low-lying ${0}_{2}^{+}$ intruder state at 639 keV, based on the coincidence with a previously unobserved 1764-keV $\ensuremath{\gamma}$ ray, and suggested it as evidence for shape coexistence in $^{80}\mathrm{Ge}$. We used the $\ensuremath{\beta}$ decay from the ${3}^{\ensuremath{-}}$ 22.4-keV state in $^{80}\mathrm{Ga}$ to enhance the population of low-spin states in $^{80}\mathrm{Ge}$, including any excited ${0}^{+}$ level, and $\ensuremath{\gamma}\ensuremath{\gamma}$ coincidences to investigate it. We observed a 1764-keV $\ensuremath{\gamma}$ ray in coincidence with strong transitions in $^{80}\mathrm{Ge}$, thus not feeding the proposed 639-keV ${0}_{2}^{+}$. No connecting transitions from previously known levels to the 639-keV and 2403-keV ${2}_{3}^{+}$ states could be established either. Shell-model calculations for Ge isotopes and $N=48$ isotones were performed. They succeed to explain most of the experimental levels, but fail to reproduce the presence of a ${0}_{2}^{+}$ state below $\ensuremath{\approx}1200$ keV in $^{80}\mathrm{Ge}$. Our experimental findings and shell-model calculations are difficult to reconcile with a very low-lying ${0}_{2}^{+}$ state in $^{80}\mathrm{Ge}$.

The structure of Ge-80 has been investigated at the ISOLDE facility at CERN. A previous study reported for the first time a low-lying 0(2)(+) intruder state at 639 keV, based on the coincidence with a previously unobserved 1764-keV gamma ray, and suggested it as evidence for shape coexistence in Ge-80. We used the beta decay from the 3(-) 22.4-keV state in Ga-80 to enhance the population of low-spin states in Ge-80, including any excited 0(+) level, and gamma gamma coincidences to investigate it. We observed a 1764-keV gamma ray in coincidence with strong transitions in Ge-80, thus not feeding the proposed 639-keV 0(2)(+). No connecting transitions from previously known levels to the 639-keV and 2403-keV 2(3)(+) states could be established either. Shell-model calculations for Ge isotopes and N = 48 isotones were performed. They succeed to explain most of the experimental levels, but fail to reproduce the presence of a 0(2)(+) state below approximate to 1200 keV in Ge-80. Our experimental findings and shell-model calculations are difficult to reconcile with a very low-lying 0(2)(+) state in Ge-80.

The beta-decay of Zn-81 to the neutron magic N = 50 nucleus Ga-81, with only three valence protons with respect to Ni-78, was investigated. The study was performed at the ISOLDE facility at CERN by means of gamma spectroscopy. The 81Zn half-life was determined to be T-1/2 = 290(4) ms while the beta-delayed neutron emission probability was measured as P-n = 23(4)%. The analysis of the beta-gated gamma-ray singles and gamma-gamma coincidences from the decay of Zn-81 provides 47 new levels and 70 new transitions in Ga-81. The beta(-)n decay of Zn-81 was observed and a new decay scheme into the odd-odd Ga-80 nucleus was established. The half-lives of the first and second excited states of Ga-81 were measured via the fast-timing method using LaBr3(Ce) detectors. The level scheme and transition rates are compared to large-scale shell-model calculations. The low-lying structure of (81)Gais interpreted in terms of the coupling of the three valence protons outside the doubly magic Ni-78 core.

V. Vedia,1,* V. Paziy,1 L. M. Fraile,1 H. Mach,1,2,† W. B. Walters,3 A. Aprahamian,4 C. Bernards,5,6 J. A. Briz,7,‡ B. Bucher,4,8 C. J. Chiara,3,9 Z. Dlouhý,10,§ I. Gheorghe,11 D. Ghiţă,11 P. Hoff,12 J. Jolie,13 U. Köster,14 W. Kurcewicz,15 R. Lică,11 N. Mărginean,11 R. Mărginean,11 B. Olaizola,1,16 J.-M. Régis,5 M. Rudigier,17 T. Sava,11 G. S. Simpson,18 M. Stănoiu,11 and L. Stroe11 1Grupo de Física Nuclear, Facultad de Ciencias Físicas, Universidad Complutense-CEI Moncloa, E-28040 Madrid, Spain 2National Centre for Nuclear Research, BP1, ul. Hoża 69, 00-681, Warsaw, Poland 3Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA 4Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, USA 5Institut für Kernphysik, Köln, Germany 6Wright Nuclear Structure Laboratory, Yale University, New Haven, Connecticut 06520, USA 7Instituto de Estructura de la Materia, CSIC, 28006 Madrid, Spain 8Lawrence Livermore National Laboratory, Livermore, California 94550, USA 9Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA 10Nuclear Physics Institute of the AS CR, Řež, Czech Republic 11“Horia Hulubei” National Institute for Physics and Nuclear Engineering, Magurele, Romania 12Department of Chemistry, University of Oslo, Oslo, Norway 13Institut für Kernphysik, Universität zu Köln, Zulpicher Strasse 77, D-50937, Köln, Germany 14Institut Laue Langevin, 71 avenue des Martyrs, 38042 Grenoble Cedex 9, France 15Faculty of Physics, University of Warsaw, Pasteura 5, PL 02-93 Warsaw, Poland 16TRIUMF, 4004 Wesbrook Mall, Vancouver, BC V6T 2A3, Canada 17Department of Physics, University of Surrey, Guildford GU2 7XH, United Kingdom 18LPSC, Université Joseph Fourier Grenoble 1, CNRS/IN2P3, Institut National Polytechnique de Grenoble,

The existence of two close-lying nuclear states in Ga-73 has recently been experimentally determined: a 1/2(-) spin-parity for the ground state was measured in a laser spectroscopy experiment, while a J(pi\) = 3/2(-) level was observed in transfer reactions. This scenario is supported by Coulomb excitation studies, which set a limit for the energy splitting of 0.8 keV. In this work, we report on the study of the excited structure of Ga-73 populated in the beta decay of Zn-73 produced at ISOLDE, CERN. Using beta-gated, gamma-ray singles, and gamma-gamma coincidences, we have searched for energy differences to try to delimit the ground-state energy splitting, providing a more stringent energy difference limit. Three new half-lives of excited states in Ga-73 have been measured using the fast-timing ;method with LaBr3(Ce) detectors. From our study, we help clarify the excited structure of Ga-73 and we extend the existing Zn-73 decay to Ga-73 with 8 new energy levels and 35 gamma transitions. We observe a 195-keV transition consistent with a gamma ray de-exciting a short-lived state in the beta-decay parent Zn-73.c

All material supplied via JYX is protected by copyright and other intellectual property rights, and duplication or sale of all or part of any of the repository collections is not permitted, except that material may be duplicated by you for your research use or educational purposes in electronic or print form. You must obtain permission for any other use. Electronic or print copies may not be offered, whether for sale or otherwise to anyone who is not an authorised user. High-sensitivity study of levels in 30Al following β decay of 30Mg Olaizola, B.; Mach, H.; Fraile, L. M.; Benito, J.; Borge, M. J. G.; Boutami, R.; Butler, P. A.; Dlouhy, Z.; Fynbo, H. O. U.; Hoff, P.; Hyldegaard, S.; Jeppesen, H. B.; Jokinen, Ari; Jollet, C.; Korgul, A.; Köster, U.; Kröll, Th.; Kurcewicz, W.; Marechal, F.; Mrazek, J.; Nilsson, T.; Płóciennik, W. A.; Ruchowska, E.; Schuber, R.; Schwerdtfeger, W.; Sewtz, M.; Simpson, G. S.; Stanoiu, M.; Tengblad, O.; Thirolf, P. G.; Yordanov, D. T.

gamma-ray and fast-timing spectroscopy were used to study levels in Al-30 populated following the beta(-) decay of Mg-30. Five new transitions and three new levels were located in Al-30. A search was made to identify the third 1(+) state expected at an excitation energy of similar to 2.5 MeV. Two new levels were found, at 3163.9 and 3362.5 keV, that are firm candidates for this state. Using the advanced time-delayed (ATD) beta gamma gamma (t) method we have measured the lifetime of the 243.8-keV state to be T-1/2 = 15(4) ps, which implies that the 243.8-keV transition is mainly of M1 character. Its fast B(M1; 2(+) -> 3(+)) value of 0.10(3) W.u. is in very good agreement with the USD shell-model prediction of 0.090 W.u. The 1801.5-keV level is the only level observed in this study that could be a candidate for the second excited 2(+) state.

The electromagnetic structure of 140 Sm was studied in a low-energy Coulomb excitation experiment with a radioactive ion beam from the REX-ISOLDE facility at CERN. The 2 + and 4 + states of the ground-state band and a second 2 + state were populated by multistep excitation. The analysis of the differential Coulomb excitation cross sections yielded reduced transition probabilities between all observed states and the spectroscopic quadrupole moment for the 2 + 1 state. The experimental results are compared to large-scale shell model calculations and beyond-mean-field calculations based on the Gogny D1S interaction with a five-dimensional collective Hamiltonian formalism. Simpler geometric and algebraic models are also employed to interpret the experimental data. The results indicate that 140 Sm shows considerable γ softness, but in contrast to earlier speculation no signs of shape coexistence at low excitation energy. This work sheds more light on the onset of deformation and collectivity in this mass region.

We propose to use fast-timing and γ spectroscopy to study five nuclei including the doubly magic Sn and its four neighbours: two-neutron hole Sn, one-neutron hole Sn, one-neutron particle Sn and two-neutron particle Sn. There is an increasing interest in these nuclei since they serve to test nuclear models using state-of-the-art interactions and many body approaches, and they provide information relevant to deduce single particle states. In addition properties of these nuclei are very important to model the astrophysical r-process. The present ISOLDE facility provides unique capabilities to study these Sn nuclei populated in the β-decay of In isomers, produced from a UCx target unit equipped with neutron converter and ionized with RILIS, capable of selective isomer ionization. The increased production yields for In are estimated to be 200 larger than in the previous work done at OSIRIS. We will use the recently commissioned Isolde Decay Station (IDS), slightly modified to improve the efficiency of fast-timing measurements. Compared to earlier measurements in this region the sensitivity will be enhanced by the use of the highly-efficient clover-type Ge detectors and the new generation fast-timing LaBr3(Ce) crystals. Requested shifts: 27 shifts (split into 1 run over 1 year) 1 Experimental and theoretical framework Doubly-magic nuclei and their immediate neighbours command a strong interest for both theoretical and experimental investigations [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]. They represent the best regions to test the shell-model effective Hamiltonian, namely the single particle energies and two-body matrix elements of the residual interaction, as well as the effective electromagnetic operators, which are then used in model calculations over an extended range of the nuclide chart. For the vast region of the medium heavy nuclei, there are only two doubly-magic nuclei, stable Pb and exotic Sn, which can be studied in greater detail. Sn isotopes are very special since those that can be studied experimentally span a long range, starting from the doubly magic Sn to Sn, and now extending even to Sn [1]. The interest in the Sn nucleus and the difficulty in accessing it, can be illustrated by the fact that in the last 20 years there were about 500 theoretical studies on this nucleus but only a few experimental investigations of its excited states. Realistic shell-model calculations have proved to lead to a good description of nuclear structure around Sn [9]. In these calculations, the two-body matrix elements of the shell-model effective Hamiltonian are constructed by means of many-body perturbation theory starting from a low-lomentum interaction derived from the high-precision CD-Bonn nucleon-nucleon potential. The chosen model space includes the 6 neutronparticle orbitals 0h9/2 1f7/2, 1f5/2, 2p3/2, 2p1/2, 0i13/2, and the 5 neutron-hole orbitals 0g7/2, 1d5/2, 1d3/2, 2s1/2, 011/2 for tin isotopes with N >82 and N<82, respectively. The values of the single-particle and single-hole energies are taken from experiment, and more precisely, whenever available, from the spectra of Sn and Sn. Proton and neutron excitations across the 50 and 82 shells are not explicitly included in the calculations but are accounted for by the core polatization contributions to the effective interaction. It is worth mentioning also that this nuclear region is important to the understanding

Electromagnetic transition strengths and spectroscopic quadrupole moments for 140 Sm were measured by means of multi-step Coulomb excitation with radioactive beam at the ISOLDE facility at CERN. A complementary experiment was performed at the Heavy Ion Laboratory in Warsaw to assign spins for non-yrast states using the angular correlation technique. Based on the new experimental data previous spin assignments need to be revised.

Electromagnetic transition strengths and spectroscopic quadrupole moments for Sm-140 were measured by means of multi-step Coulomb excitation with radioactive beam at the ISOLDE facility at CERN. A complementary experiment was performed at the Heavy Ion Laboratory in Warsaw to assign spins for non-yrast states using the angular correlation technique. Based on the new experimental data previous spin assignments need to be revised.

The neutron-rich nucleus 81Ga was populated from the β-decay of 81Zn produced at the ISOLDE (CERN) facility. The analysis of β-gated γ-ray singles and γ-γ coincidences permits to extend significantly the level scheme of 81Ga as well as to provide a new half-life for 81Zn. A preliminary upper limit was obtained for the half-life of the first excited state in 81Ga.

A new level scheme of Ga-80 has been determined. This nucleus was populated following the beta(-) decay of Zn-80 at ISOLDE, CERN. The proposed level scheme is significantly different compared to the previously reported one and contains 26 levels up to 3.4 MeV in excitation energy. The present study establishes that the previously identified 1.9-s beta(-)-decaying 6(-) isomer is the ground state of 80Ga and the 1.3-s beta(-)-decaying 3(-) isomer lies at an excitation energy of 22.4 keV. A new isomeric level was identified at 707.8 keV and its half-life was measured to be 18.3(5) ns, allowing the 685.4-keV transition de-exciting this state to be assigned an M2 multipolarity. The newly measured spectroscopic observables are compared with shell-model calculations using the jj44bpn and JUN45 interactions.

A new level scheme of Ga80 has been determined. This nucleus was populated following the β− decay of Zn80 at ISOLDE, CERN. The proposed level scheme is significantly different compared to the previously reported one and contains 26 levels up to 3.4 MeV in excitation energy. The present study establishes that the previously identified 1.9-s β−-decaying 6− isomer is the ground state of Ga80 and the 1.3-s β−-decaying 3− isomer lies at an excitation energy of 22.4 keV. A new isomeric level was identified at 707.8 keV and its half-life was measured to be 18.3(5) ns, allowing the 685.4-keV transition de-exciting this state to be assigned an M2 multipolarity. The newly measured spectroscopic observables are compared with shell-model calculations using the jj44bpn and JUN45 interactions.Received 27 May 2014DOI:https://doi.org/10.1103/PhysRevC.90.014320©2014 American Physical Society

We report on the results of the beta-decay of Zn-81. The experiment was performed at the CERN ISOLDE facility in the framework of a systematic ultra-fast timing(1) investigation of neutron-rich nuclei populated in the decay of Zn. The present analysis included beta-gated gamma-ray singles and gamma-gamma coincidences from the decay of Zn-81 to Ga-81 and leads to a new and much more extensive level scheme of Ga-81. A new half-life of Zn-81 is provided.

We propose to study spectroscopic quadrupole moments of excited states and electromagnetic transition rates between them in the neutron-deficient rare earth nuclei Sm and Gd using projectile Coulomb excitation at energies of 4.7 MeV per nucleon. The rare earth nuclei below the N=82 shell closure form one of the few regions of the nuclear chart where oblate shapes are expected to occur near the ground state. Nuclear shapes are expected to change rapidly in this region, with coexistence of oblate and prolate shapes in some nuclei. The measurement of electromagnetic matrix elements represents therefore a particularly sensitive test of theoretical nuclear structure models. Requested shifts: 24 shifts, split into 2 runs (12 shifts for Sm and 12 shifts for Gd) Beamline: MINIBALL + CD-only

A new level scheme was constructed for Ga-80 which is significantly different from the one previously reported [1]. The excitation energy of a new low-lying state recently reported in [2] was identified at 22.4 keV. Properties of the level scheme suggest that the ground state has spin J = 6 and the first excited state has spin J = 3. The spin assignments are in agreement with laser spectroscopy values previously measured [2]. Our work provides the first evidence for the J = 6 being the ground state.

We propose to start a program to study the gamma-ray strength function of neutron rich nuclei in inverse kinematics with radioactive beams at HIE-ISOLDE. An unexpected increase in the gamma strength function at low energy has been observed in several stable nuclei using the Oslo method. This year these results were confirmed with a different experimental technique and model independent analysis developed by iThemba/Livermore. If this enhancement of the gamma strength function is also present in neutron rich nuclei, it will strongly affect the neutron capture cross sections, which are important input in stellar models of synthesis of heavier elements in stars. We propose to start with an experiment using a Ni beam of 5.5 MeV/u, where the data will be analyzed using both methods independently, and we are sure to get enough statistics, before moving to more neutron rich nuclei. When/if neutron rich Ti, Fe or Mo beams will be available at ISOLDE we will submit additional proposals.

We performed at ISOLDE the spectroscopy of the decay of the 8- isomer in 136Cs by and conversion-electron detection. For the first time the excitation energy of the isomer and the multipolarity of its decay have been measured. The half-life of the isomeric state was remeasured to T1/2 = 17.5(2) s. This isomer decays via a very slow 518 keV E3 transition to the ground state. In addition to this, a much weaker decay branch via a 413 keV M4 and a subsequent 105 keV E2 transition has been found. Thus we have found a new level at 105 keV with spin 4+ between the isomeric and the ground state. The results are discussed in comparison to shell model calculations.