Search

Reduced transition strengths of the deexciting transitions from the first two excited states in 33Ar were measured in a relativistic Coulomb excitation experiment at the GSI Helmholtz center. The radioactive ion beam was produced by fragmentation of a primary 36Ar beam on a 9Be target followed by the selection of the reaction product of interest via the GSI Fragment Separator. The 33Ar beam hit a secondary 197Au 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 γ -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 33Ar the reduced transition strengths have been determined. With these first results the Tz = −3/2 nucleus 33Ar is now, together with 21Na (Tz = −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

The β-decay half-lives of 110 neutron-rich isotopes of the elements from _{37}Rb to _{50}Sn were measured at the Radioactive Isotope Beam Factory. The 40 new half-lives follow robust systematics and highlight the persistence of shell effects. The new data have direct implications for r-process calculations and reinforce the notion that the second (A≈130) and the rare-earth-element (A≈160) abundance peaks may result from the freeze-out of an (n,γ)⇄(γ,n) equilibrium. In such an equilibrium, the new half-lives are important factors determining the abundance of rare-earth elements, and allow for a more reliable discussion of the r process universality. It is anticipated that universality may not extend to the elements Sn, Sb, I, and Cs, making the detection of these elements in metal-poor stars of the utmost importance to determine the exact conditions of individual r-process events.

The structure of the neutron-rich bismuth isotope 217Bi has been studied for the first time. The fragmentation of a primary 238U beam at the FRS-RISING setup at GSI was exploited to perform γ-decay spectroscopy, since μs isomeric states were expected in this nucleus. Gamma rays following the decay of a t1/2=3 μs isomer were observed, allowing one to establish the low-lying structure of 217Bi. The level energies and the reduced electric quadrupole transition probability B(E2) from the isomeric state are compared to large-scale shell-model calculations.

International audience; Preliminary results are presented from a recent campaign of experiments,performed at the PF1B cold-neutron facility at ILL (Grenoble,France), in which $\gamma$-ray spectroscopy of neutron-rich nuclei produced inneutron induced fission on 235U and 241Pu targets was performed. By usingthe EXILL array, consisting of EXOGAM, GASP and ILL-Cloverdetectors, and a digital triggerless data acquisition system, coincidences over several microseconds time windows were studied. This allowed to obtainnew information on nuclei around 132Sn, such as 132Te, 133Sb and130Sn, in which microsecond isomeric states occur. Preliminary results on210Bi, populated by cold-neutron capture, are also shown. The data offerthe possibility to investigate the couplings between core excitations andvalence particles, around the doubly magic nuclei 132Sn and 208Pb.

Search for a new kind of superfluidity built on collective proton-neutron pairs with aligned spin is performed studying the Gamow-Teller decay of the T=1, Jπ=0+ ground state of Ge62 into excited states of the odd-odd N=Z nucleus Ga62. The experiment is performed at GSI Helmholtzzentrum fur Schwerionenforschung with the Ge62 ions selected by the fragment separator and implanted in a stack of Si-strip detectors, surrounded by the RISING Ge array. A half-life of T1/2=82.9(14) ms is measured for the Ge62 ground state. Six excited states of Ga62, populated below 2.5 MeV through Gamow-Teller transitions, are identified. Individual Gamow-Teller transition strengths agree well with theoretical predictions of the interacting shell model and the quasiparticle random phase approximation. The absence of any sizable low-lying Gamow-Teller strength in the reported beta-decay experiment supports the hypothesis of a negligible role of coherent T=0 proton-neutron correlations in Ga62. (Less)

The shape transition in the neutron-rich Os isotopes is studied by investigating the neutron-rich 196Os nucleus through in-beam γ-ray spectroscopy using a two-proton transfer reaction from a 198Pt target to a 82Se beam. The beam-like recoils were detected and identified with the large-acceptance magnetic spectrometer PRISMA, and the coincident γ rays were measured with the advanced gamma tracking array (AGATA) demonstrator. The de-excitation of the low-lying levels of the yrast-band of 196Os were identified for the first time. The results are compared with state-of-the-art beyond-mean-field calculations, performed for the even-even 188-198Os isotopes. The new results suggest a smooth transition in the Os isotopes from a more axial rotational behavior towards predominately vibrational nuclei through triaxial configurations. An almost perfect γ-unstable/triaxial rotor yrast band is predicted for 196Os which is in agreement with the experimentally measured excited states

This Letter reports on a systematic study of β-decay half-lives of neutron-rich nuclei around doubly magic Pb208. The lifetimes of the 126-neutron shell isotone Pt204 and the neighboring Ir200-202, Pt203, Au204 are presented together with other 19 half-lives measured during the "stopped beam" campaign of the rare isotope investigations at GSI collaboration. The results constrain the main nuclear theories used in calculations of r-process nucleosynthesis. Predictions based on a statistical macroscopic description of the first-forbidden β strength reveal significant deviations for most of the nuclei with N

This paper reports NMR measurements of the magnetic dipole moments of two high-K isomers, the 37/2-, 51.4 m, 2740 keV state in Hf177 and the 8-, 5.5 h, 1142 keV state in Hf180 by the method of on-line nuclear orientation. Also included are results on the angular distributions of γ transitions in the decay of the Hf177 isotope. These yield high precision E2/M1 multipole mixing ratios for transitions in bands built on the 23/2+, 1.1 s, isomer at 1315 keV and on the 9/2+, 0.663 ns, isomer at 321 keV. The new results are discussed in the light of the recently reported finding of systematic dependence of the behavior of the gR parameter upon the quasiproton and quasineutron make up of high-K isomeric states in this region. © 2014 American Physical Society.

5 pags. ; 3 figs. ; PACS numbers: 23.40.-s, 21.10.Pc, 27.60.+j, 21.60.Cs ; Taprogge, J., et al.

To study the β-decay properties of some well known delayed neutron emitters an experiment was performed in 2009 at the IGISOL facility (University of Jyvaskyla in Finland) using Total Absorption -ray Spectroscopy (TAGS) technique. The aim of these measurements is to obtain the full β-strength distribution below the neutron separation energy (Sn) and the γ/neutron competition above. This information is a key parameter in nuclear technology applications as well as in nuclear astrophysics and nuclear structure. Preliminary results of the analysis show a significant γ-branching ratio above Sn. © Owned by the authors, published by EDP Sciences, 2014.

Energy correlations between gamma -ray transitions and the prompt proton decay line in Cu-58 were studied by means of the fusion-evaporation reaction Ca-40(Mg-24,1 alpha 1p1n) using the EUROBALL spectrometer coupled to ancillary detector devices. A lifetime of 0.06 < tau < 0.58 ps for the 8915 keV proton-decaying state in Cu-58 is deduced. (C) 2001 Elsevier Science B.V. All rights reserved.

We report results from a pioneering experiment to measure the g factors of isomeric states of neutron-rich nuclei around 68Ni, far from the valley of β stability.For the first time, the time-dependent perturbed angular distribution method was applied in combination with the heavy-ion-γ correlation technique to study g factors of spin-aligned isomers produced in a projectile fragmentation reaction and mass-separated. Some technical aspects are discussed and illustrated with preliminary results.

We present results on the isomer spectroscopy of a number of neutron-rich rare earth and transitional elements with A N 190 200, following the projectile fragmentation of a 1 GeV per nucleon ‘08Pb beam. The technique was sensitive to decays from metastable states with lifetimes in the nanoto millisecond time range. The nuclei of interest were separated and unambiguously identified on an event-by-event basis using the Fragment Separator at GSI. The analysis allows a clear differentiation between ions of different charge states and places a new lower limit of -15 ns, on the lifetimes of isomers which have been studied using this technique.

P. Chowdhury”, I. Shestakova”, R. D’Alarcaoa, C.J. Pearsonb, Z. Podolyakb, P.M. Walkerb, C. Wheldonb, D.M. Cullenc, I. Ahmadd, M.P. Carpenterd, R.V.F. Janssensd, T.L. Khood, F.G. Kondevd, C.J. Listerd, D. Seweryniakd and I. Wiedenhoeverd aDepartment of Physics, University of Massachusetts, Lowell, MA 01854, USA bDepartment of Physics, University of Surrey, Guildford GU2 5XH, UK ‘Department of Physics, Oliver Lodge Laboratory, University of Liverpool, Liverpool L69 7ZE, UK dArgonne Na tl ‘o nal Laboratory, Argonne, IL 60439, USA New multi-quasiparticle K-isomers have been investigated in neutron-rich hafnium nu- clei via inelastic and transfer reactions with a pulsed 238U beam on a lsoHf target. The emphasis of this presentation is on the specific techniques of isolating and characteriz- ing isomers with 2~s half-lives and low cross-sections in the transfer channels using the Gammasphere array. 1. THE PHYSICS Quantum numbers associated with special symmetries of the nuclear wave-function in- vite investigation regarding their limits of validity. One that has received considerable attention now for a number of years is K, the

Rotational states assigned to a Kπ = ({5}+) band in 18071Lu109 have been populated in the decay of a t1/2≥1 ms, two-quasiparticle isomer. Delayed γ-ray and x-ray coincidences were observed with the Gammasphere array following the deep-inelastic reaction 23892U + 18072Hf. Gamma-ray coincidence and intensity data, comparisons with the level structure of the neighbouring odd-odd isotone, a g-factor analysis and theoretical predictions of multi-quasiparticle states, all support the assignment of the new band to the neutron-rich nucleus 180Lu.

The g factors of the 7 2 + 235 keV isomer in 175W and the 14+ 3746 keV isomer in 176W have been measured by observing the precession of the decay γ-ray angular distribution in an external magnetic field as g 7 2 + , 175 W =−0.187(6) and g(14 + , 176 W )=+0.475(15) . A pure wave function has been assigned to the Kπ=14+ isomer from comparison with predictions based on experimental g factors of deformed single-particle orbitals in this mass region. The value gR=0.27(2) has been deduced for the rotational g factor by using the measured g factor of the 14+ state and the branching ratios in the associated band.

The lifetime andthe γ-decay to the 0+ groundstate of the lowest 3− state in 148Gd has been determined. The reduced strength B(E3, 3− → 0+)=41 (6) W.u. agrees well with the theoretical value from empirical shell model calculations and can be directly compared with the 12+ → 9− two-octupole-phonon → one-octupole-phonon strength obtained in the same Recoil Distance Method lifetime measurement. The results of our search for a three octupole-phonon state built on the (νf 7/2) 6+ 2 state is also reported.

High-spin rotational structures in the odd-odd nuclei 130,132Pr have been studied via the 104 Pd + 32 S reaction at 160 MeV. Several states below the previously reported negative- and positive-parity states have been established through the observation of low-energy transitions, leading to new spin assignments for all observed levels. The bands based on the πh 11 2 ⊗ vg 7 2 and πh 11 2 ⊗ vh 11 2 configurations have been extended at much higher spins. Detailed interacting boson-fermion-fermion model calculations have been performed for the two nuclei, which reveal the complex structure of the new observed low-lying states. The change from inverted to normal signature at high spin and the staggering pattern of all observed bands are well reproduced, being explained by the interplay between a new term introduced in the boson quadrupole operator and the residual quadrupole-quadrupole interaction.

The quadrupole moments of highly deformed bands in ${}^{134,135}\mathrm{Nd}$ and ${}^{131}\mathrm{Ce}$ have been determined using the Doppler-shift attenuation method. The obtained ${Q}_{0}$ values show no clear dependence on the number of occupied $\ensuremath{\nu}{i}_{13/2}$ intruder orbitals. Cranked shell model calculations indicate that the charge-quadrupole moments of the highly deformed bands decrease with increasing spin. The expected increase in deformation induced by the $\ensuremath{\nu}{i}_{13/2}$ orbital in two bands of ${}^{134}\mathrm{Nd}$ is attenuated by a rotation-induced shrinking effect driving the nucleus towards smaller deformation.

Deep-inelastic collisions of a 208Pb beam on a 208Pb target were performed using the ATLAS accelerator at Argonne National Laboratory. The Gammasphere detector array was used for the detection of prompt and delayed gamma-rays of the reaction products.207Tl is one proton away from the 208Pb doubly-magic nucleus. Its low-energy level structure is dominated by the single proton-hole states πs1/2−1, πd3/2−1 and πh11/2−1. The 11/2− state is isomeric with T1/2 = 1.33(11) s. The reaction partner of 207Tl is 209Bi, which has arelatively well established level scheme compared to 207Tl. Cross-coincidences between these two nuclei were used to confirm or establish levels above the 11/2− isomeric state in 207Tl. These states are obtained via breaking of the neutron core. Angular correlation analysis was performed on known transitions in 208Pb, proving the applicability of this method for multipolarity assignment.

New positive-parity states, having a bandlike structure, were observed in $^{105}\mathrm{Ru}$. The nucleus was produced in an induced fission reaction, and the prompt $\ensuremath{\gamma}$-rays, emitted from the fragments, were detected by the EUROBALL III multidetector array. The partial scheme of excited $^{105}\mathrm{Ru}$ levels is analyzed within the triaxial-rotor-plus-particle approach.

25th International Nuclear Physics Conference, Florence, Italy, 2 Jun 2013 - 7 Jun 2013; The European physical journal / Web of Conferences Web of Conferences : proceedings proceedings 66, 02043 (2014). doi:10.1051/epjconf/20146602043, Published by EDP Sciences, Les Ulis

The fragmentation of relativistic uranium projectiles has been exploited at the Gesellschaft fur Schwerionenforschung laboratory to investigate the β decay of neutron-rich nuclei just beyond 208Pb. This paper reports on β-delayed γ decays of 211-213Tl, 215Pb, and 215-219Bi de-exciting states in the daughters 211-213Pb, 215Bi, and 215-219Po. The resulting partial level schemes, proposed with the help of systematics and shell-model calculations, are presented. The role of allowed Gamow-Teller and first-forbidden β transitions in this mass region is discussed. © 2014 American Physical Society.

G. Guastalla, et al. XX International School on Nuclear Physics, Neutron Physics and Applications (Varna 2013); 5 pags.; 1 fig., The analysis of the Coulomb excitation experiment conducted on 104Sn required a strict selection of the data in order to reduce the large background present in the γ-ray energy spectra and identify the γ-ray peak corresponding to the Coulomb excitation events. As a result the B(E2; 0+ →2+) value could be extracted, which established the downward trend towards 100Sn and therefore the robustness of the N=Z=50 core against quadrupole excitations. Published under licence by IOP Publishing Ltd, A. J. would like to thank the Spanish Ministerio de Ciencia e Innovacion for financial support under Contract No. FPA2011-29854- C04

The reaction {sup 58}Ni({sup 28}Si,2n{gamma}) at 90 MeV incident energy has been used to populate the N=Z nucleus {sup 84}Mo. The GASP array was used together with the ISIS Silicon ball, which allowed a subtraction of the charged particle channels in the {gamma}-{gamma} coincidences. The only known transition 2{sub 1}{sup +}{r_arrow}0{sub 1}{sup +} of 443.8 keV in {sup 84}Mo has been found in coincidence with a {gamma} ray of 673.5{plus_minus}0.4 keV which was assigned as the second (4{sub 1}{sup +}{r_arrow}2{sub 1}{sup +}) yrast transition. The behavior of the resulting yrast line indicates that {sup 84}Mo is a transitional nucleus. The correlation between the excitation energies of the 2{sub 1}{sup +} and 4{sub 1}{sup +} levels of the N=Z nuclei reveals a systematic deviation from the average behavior defined by all collective even-even nuclei. {copyright} {ital 1997} {ital The American Physical Society}

Three bands consisting of dipole M1 and quadrupole E2 crossover transitions have been identified in 134 Nd using the GASP array and the 110 Pd( 28 Si, 4n) reaction at 130 MeV. Calculations with the projected shell model are used to assign configurations to the different bands and to infer their K -composition. The properties of the band built on the I π = 8 − isomer confirm the previously assigned two-quasineutron [404] 7 2 + ⊗ [514] 9 2 − configuration of the isomeric state. The other two bands are interpreted as coexisting prolate and oblate four-quasiparticle configurations.

In a nuclear reactor, the decay of fission fragments is at the origin of decay heat and antineutrino flux. These quantities are not well known while they are very important for reactor safety and for our understanding of neutrino physics. One reason for the discrepancies observed in the estimation of the decay heat and antineutrinos flux coming from reactors could be linked with the Pandemonium effect. New measurements have been performed at the JYFL facility of Jyvaskyla with a Total Absorption Spectrometer (TAS) in order to circumvent this effect. An overview of the TAS technique and first results from the 2009 measurement campaign will be presented. © Owned by the authors, published by EDP Sciences, 2013.

A range of high resolution gamma-ray spectroscopy measurements have been carried out using arrays which include a number of Cerium-doped Lanthanum-Tribromide (LrBr3 (Ce)) scintillation detectors used in conjunction with high-resolution hyper-pure germanium detectors. Examples of the spectral and temporal responses of such set-ups, using both standard point radioactive sources 152 Eu and 56 Co, and in-beam fusionevaporation reaction experiments for precision measurements of nuclear excited states in 34 P and 138 Ce are presented. The current and future use of such arrays at existing (EURICA at RIKEN) and future (NUSTAR at FAIR) secondary radioactive beam facilities for precision measurements of excited nuclear state lifetimes in the 10 ps to 10 ns regime are also discussed.

Lifetimes of the low-lying (11/2-) states in 63,65Co have been measured employing the recoil distance doppler shift method (RDDS) with the AGATA γ-ray array and the PRISMA mass spectrometer. These nuclei were populated via a multinucleon transfer reaction by bombarding a 238U target with a beam of 64Ni. The experimental B(E2) reduced transition probabilities for 63,65Co are well reproduced by large-scale shell-model calculations that predict a constant trend of the B(E2) values up to the N=40 67Co isotope

The level structures of the very neutron-rich nuclei $^{128}\mathrm{Pd}$ and $^{126}\mathrm{Pd}$ have been investigated for the first time. In the $r$-process waiting-point nucleus $^{128}\mathrm{Pd}$, a new isomer with a half-life of $5.8(8)\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$ is proposed to have a spin and parity of ${8}^{+}$ and is associated with a maximally aligned configuration arising from the ${g}_{9/2}$ proton subshell with seniority $\ensuremath{\upsilon}=2$. For $^{126}\mathrm{Pd}$, two new isomers have been identified with half-lives of 0.33(4) and $0.44(3)\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$. The yrast ${2}^{+}$ energy is much higher in $^{128}\mathrm{Pd}$ than in $^{126}\mathrm{Pd}$, while the level sequence below the ${8}^{+}$ isomer in $^{128}\mathrm{Pd}$ is similar to that in the $N=82$ isotone $^{130}\mathrm{Cd}$. The electric quadrupole transition that depopulates the ${8}^{+}$ isomer in $^{128}\mathrm{Pd}$ is more hindered than the corresponding transition in $^{130}\mathrm{Cd}$, as expected in the seniority scheme for a semimagic, spherical nucleus. These experimental findings indicate that the shell closure at the neutron number $N=82$ is fairly robust in the neutron-rich Pd isotopes.

${}^{116}\mathrm{Ru}$ and ${}^{118}\mathrm{Ru}$ have been studied via $\ensuremath{\beta}$-delayed $\ensuremath{\gamma}$-ray spectroscopy of nuclei produced in fragmentation reactions at the Radioactive Ion-Beam Factory (RIBF) facility. Level schemes with positive-parity states up to spin $J=6$ have been constructed. The results have been discussed in terms of the interacting boson model, the algebraic collective model, and total Routhian surfaces. We conclude that the very neutron-rich nuclei still show many features associated with triaxial $\ensuremath{\gamma}$-soft nuclei, represented by the O(6) symmetry, but are approaching a spherical structure, the U(5) symmetry, with increasing neutron number towards the $N=82$ shell closure. In ${}^{118}\text{Ru}$, hints of a shape transition in the ground state have been observed.

The beta decay of five heavy, neutron-rich nuclei, Pt-203,Pt-204 and Ir200-202, has been investigated following relativistic cold fragmentation reactions of lead projectiles using the FRS + RISING setup at GSI. This paper reports on the study of the low-lying states in the decay daughter nuclei Au-203,Au-204 and Pt200-202. The characteristic gamma rays for each nucleus have been determined using beta-delayed gamma-ray spectroscopy. Tentative level schemes, relative intensities, and apparent beta feedings are provided. These data are compared with shell-model calculations, which indicate a substantial contribution to the total beta strength from high-energy first-forbidden beta-decay transitions in this mass region.

Isomeric ratios have been measured for high-spin states in Po-198,200,206,208(84), At-208,209,210,211(85), Rn-210,211,212,213,214(86), Fr-208,211,212,213,214(87), Ra-210,211,212,214,215(88), and Ac-215(89) following the projectile fragmentation of a 1 AGeV U-238 beam by a Be-9 target at GSI Helmholtzzentrum fur Schwerionenforschung. The fragments were separated in the fragment separator (FRS) and identified by means of energy loss and time-of-flight techniques. They were brought to rest at the centre of the RISING gamma-ray detector array and intensities of gamma rays emitted in the decay of isomeric states with half-lives between 100 ns and 40 mu s and spin values up to 55/2 (h) over bar were used to obtain the corresponding isomeric ratios. The data are compared to theoretical isomeric ratios calculated in the framework of the abrasion-ablation model. Large experimental enhancements are obtained for high-spin isomers in comparison to expected values. (C) 2013 Elsevier B.V. All rights reserved.

International audience; The study of β-delayed neutron emission plays a major role in different fields such as nuclear technology, nuclear astrophysics and nuclear structure. However the quality of the existing experimental data nowadays is not sufficient for the various technical and scientific applications and new high precision measurements are necessary to improve the data bases. One key aspect to the success of these high precission measurements is the use of a very pure ion beam that ensures that only the ion of interest is produced. The combination of the IGISOL mass separator with the JYFLTRAP Penning trap is an excellent tool for this type of measurement because of the ability to deliver isobarically and even isomerically clean beams. Another key feature of the installation is the non-chemical selectivity of the IGISOL ion source which allows measurements in the important region of refractory elements. This paper summarises the β-delayed neutron emission studies that have been carried out at the IGISOL facility with two different neutron detectors based on 3He counters in a polyethylene moderator: the Mainz neutron detector and the BEta deLayEd Neutron detector.

International audience; The neutron-rich isotopes of tungsten, osmium and platinum have different shapes in their ground states and present also shape transitions phenomena. Spectroscopic information for these nuclei is scarce and often limited to the gamma rays from the decay of isomeric states. For the neutron-rich even-even osmium isotopes Os-194 and Os-198, a shape transition between a slightly prolate deformed to an oblate deformed ground state was deduced from the observed level schemes. For the even-even nucleus lying in between, Os-196, no gamma ray transition is known. In order to elucidate the shape transition and to test the nuclear models describing it, this region was investigated through gamma-ray spectroscopy using the AGATA demonstrator and the large acceptance heavy-ion spectrometer PRISMA at LNL, Italy. A two-nucleon transfer from a Pt-198 target to a stable Se-82 beam was utilized to populate medium-high spin states of Os-196. The analysis method and preliminary results, including the first life-time measurement of isomeric states with AGATA, are presented.

β-decay properties of fission products are very important for applied reactor physics, for instance to estimate the decay heat released immediately after the reactor shutdown and to estimate the ν flux emitted. An accurate estimation of the decay heat and the ν emitted flux from reactors, are necessary for purposes such as reactors operation safety and non-proliferation. In order to improve the precision in the prediction for these quantities, the bias due to the Pandemonium effect affecting some important fission product data has to be corrected. New measurements of fission products β-decay, not sensitive to this effect, have been performed with a Total Absorption Spectrometer (TAS) at the JYFL facility of Jyvaskyla. An overview of the TAS technique and first results from the 2009 campaign will be presented. © Owned by the authors, published by EDP Sciences, 2014.

A measurement of the reduced transition probability for the excitation of the ground state to the first 2+ state in 104Sn has been performed using relativistic Coulomb excitation at GSI. 104Sn is the lightest isotope in the Sn chain for which this quantity has been measured. The result is a key point in the discussion of the evolution of nuclear structure in the proximity of the doubly magic nucleus 100Sn. The value B(E2; 0+ → 2+) = 0.10(4) e2b2 is significantly lower than earlier results for 106Sn and heavier isotopes. The result is well reproduced by shell model predictions and therefore indicates a robust N = Z = 50 shell closure.

Long-lived isomers in 212Bi have been studied following 238U projectile fragmentation at 670 MeV per nucleon. The fragmentation products were injected as highly charged ions into the GSI storage ring, giving access to masses and half-lives. While the excitation energy of the first isomer of 212Bi was confirmed, the second isomer was observed at 1478(30) keV, in contrast to the previously accepted value of >1910 keV. It was also found to have an extended Lorentz-corrected in-ring halflife >30 min, compared to 7.0(3) min for the neutral atom. Both the energy and half-life differences can be understood as being due a substantial, though previously unrecognised, internal decay branch for neutral atoms. Earlier shell-model calculations are now found to give good agreement with the isomer excitation energy. Furthermore, these and new calculations predict the existence of states at slightly higher energy that could facilitate isomer de-excitation studies., published in PRL 110, 122502

Neutron-rich silver isotopes were populated in the fragmentation of a 136Xe beam and the relativistic fission of 238U. The fragments were mass analyzed with the GSI Fragment Separator and subsequently implanted into a passive stopper. Isomeric transitions were detected by 105 high-purity germanium detectors. Eight isomeric states were observed in 122-126Ag nuclei. The level schemes of 122,123,125Ag were revised and extended with isomeric transitions being observed for the first time. The excited states in the odd-mass silver isotopes are interpreted as core-coupled states. The isomeric states in the even-mass silver isotopes are discussed in the framework of the proton-neutron split multiplets. The results of shell-model calculations, performed for the most neutron-rich silver nuclei are compared to the experimental data. © 2013 American Physical Society., Spanish Ministerio de Ciencia e Innovación under conctracts FPA2009-13377-C02-02 and FPA2011-29854-C04-01 and the Spanish Consolider-Ingenio 2010 Programme CPAN (CSD2007-00042).

The half-life of the Iπ=6+ yrast state at Ex=2294 keV in 138Ce has been measured as T1/2=880(19) ps using the fast-timing γ-ray coincidence method with a mixed LaBr3(Ce)-HPGe array. The excited states in 138Ce have been populated by the 130Te(12C,4n) fusion-evaporation reaction at an incident beam energy of 56 MeV. The extracted B(E2;61+→41+)=0.101(24) W.u. value is compared with the predictions of truncated basis shell model calculations and with the systematics of the region. This shows an anomalous behavior compared to the neighboring isotonic and isotopic chains. Half-lives for the yrast 5-, 11+ and 14+ states in 138Ce have also been determined in this work.

The level structures of the very neutron-rich nuclei 128Pd and 126Pd have been investigated for the first time. In the r-process waiting-point nucleus 128Pd, a new isomer with a half-life of 5.8(8) μs is proposed to have a spin and parity of 8(+) and is associated with a maximally aligned configuration arising from the g(9/2) proton subshell with seniority υ=2. For 126Pd, two new isomers have been identified with half-lives of 0.33(4) and 0.44(3) μs. The yrast 2(+) energy is much higher in 128Pd than in 126Pd, while the level sequence below the 8(+) isomer in 128Pd is similar to that in the N=82 isotone 130Cd. The electric quadrupole transition that depopulates the 8(+) isomer in 128Pd is more hindered than the corresponding transition in 130Cd, as expected in the seniority scheme for a semimagic, spherical nucleus. These experimental findings indicate that the shell closure at the neutron number N=82 is fairly robust in the neutron-rich Pd isotopes.

Understanding the β-decay properties of fission products is very important for nuclear reactor monitoring & safety. Indeed, the β-decay of fission products is a source of power during nuclear reactor operation and after, this activity is the main contributor to the decay-heat representing ∼7–8% of a reactor nominal power. β-decay is also at the origin of the antineutrinos coming from nuclear reactor. The study of antineutrinos is mandatory for nuclear safeguard policies based on antineutrino detection. But there are still some discrepancies in the calculation of the decay-heat and antineutrino spectra. One reason of the distortions observed seems to be linked to the Pandemonium effect. In order to improve the accuracy in the prediction of these quantities, new measurements of fission products β-decay properties, not sensitive to this effect, have been performed with a Total Absorption spectrometer (TAS). An overview of the TAS technique and first results from the latest experiment will be presented.

Neutron-rich nuclei in the lead region, beyond N = 126, have been studied at the FRS-RISING setup at GSI, exploiting the fragmentation of a primary uranium beam. Two isomeric states have been identified in Hg-210: the 8(+) isomer expected from the seniority scheme in the vg(9/2) shell and a second one at low spin and low excitation energy. The decay strength of the 8(+) isomer confirms the need of effective three-body forces in the case of neutron-rich lead isotopes. The other unexpected low-lying isomer has been tentatively assigned as a 3(-) state, although this is in contrast with theoretical expectations. (C) 2013 Elsevier B.V. All rights reserved.

Preliminary results of the data analysis of the beta decay of 94Rb using a novel - segmented- total absorption spectrometer are shown in this contribution. This result is part of a systematic study of important contributors to the decay heat problem in nuclear reactors. In this particular case the goal is to determine the beta intensity distribution below the neutron separation energy and the gamma/beta competition above.

γ-ray, γγ-coincidence, internal conversion electron and γ-ray angular distribution spectra of the 70 Ge(p,nγ) 70 As reaction were measured with Ge(HP) γ and superconducting magnetic lens plus Si(Li) electron spectrometers at eight bombarding proton energies between 7.59 and 8.7 MeV. Energies and relative intensities of 113 (among them 60 new) 70 As γ rays, as well as 29 new internal conversion coefficients were determined. The proposed level scheme contains 16 new levels. γ-ray branching and mixing ratios, level spin and parity values have been deduced. The spins and parities have been determined on the basis of decay properties of levels, internal conversion coefficients, Hauser-Feshbach analysis of reaction cross sections, γ-ray angular distribution and other data. The energy spectra and electromagnetic moments were calculated in the framework of the interacting boson-fermion-fermion/truncated quadrupole phonon model for odd-odd nuclei and reasonable agreement has been obtained between the experimental and theoretical results.

The empirical effective proton-neutron interaction was investigated in the singly closed shell region. It was found that the quadrupole component of the effective interaction is about twice as strong in this region as in the doubly magic one. The presence of the additional quadrupole-quadrupole interaction was explained as the first experimental evidence for the existence of the polarization interaction predicted by Bohr and Mottelson as a second order consequence of the particle-vibration coupling. It was shown that the renormalization of higher order multipole coefficients is also necessary to take into account all effects of the particle-vibration coupling. We pointed out that this renormalization can be approximated by lengthening the range of the effective interaction.

We present results from stopped beam rare isotope spectroscopic investigations at the GSI (RISING) experiment based on the detection of gamma-ray transitions following the beta decay of Pd-94. A comparison between the measured low-lying level scheme of Rh-94 and the prediction from shell-model calculations reveals the important roles of the g(7/2) and g(9/2) orbitals in explaining the structural features. The low values of the Gamow-Teller strengths B(GT) can be attributed to the influence of the neutron-proton interaction, which gives rise to an increased seniority mixing for the nuclear states, thereby leading to a fragmentation of the strength to several daughter levels. These results provide further strong indications that Pd-94 resides in the middle of a structural transition region in the Pd isotopes as the N = Z line is approached.

The half-life of a ${K}^{\ensuremath{\pi}}={12}^{+}$ isomer in ${}^{164}$Er has been measured to be 68(2) ns, and new decay pathways have been identified. These include highly $K$-forbidden $\ensuremath{\gamma}$-ray transitions directly to the ground-state rotational band, with reduced hindrance values that can be compared with those found for heavier nuclides. The new data support the interpretation that the level density is a key variable in determining $K$-forbidden transition rates.

The neutron-rich nuclei 109Pd and 111Pd were produced as fission fragments following the 30Si+168Er reaction at 142 MeV. Using the identification based on the coincidences with the complementary fission fragments, the only positive-parity bands observed so far in 109Pd and 111Pd emerged from this work. A band, built on top of the 5/2+ ground state exhibiting ΔI=1 energy-level staggering, was observed in each of these nuclei. Both nuclei of interest, 109Pd and 111Pd, are suggested to lie in the transitional region of Pd isotopes of maximum γ softness. The ground states of both nuclei are predicted by total Routhian surface calculations to be extremely γ soft with shallow triaxial minima. The first crossing in the new bands is proposed to be attributable to an alignment of h11/22 neutrons.