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International audience; Excited states of the neutron-rich Br89 have been observed for the first time. They were populated in cold-neutron induced fission of U235 at the PF1B facility of the Institut Laue-Langevin, Grenoble. The measurement of γ radiation following fission has been performed using the EXILL array of Ge detectors. The observed level structure looks similar to the yrast level structure of Br87. Large valence space shell model calculations performed for Br89 confirmed this similarity. Comparison of the observed πg9/2 band with the results of the shell model calculations provides information on the evolution of collectivity in this region.

The gyromagnetic factor of the low-lying Ex=684.10(19)keV isomeric state of the nucleus 99Mo was measured using the time-dependent perturbed angular distribution technique. This level is assigned a spin and parity of Jπ=11/2−, with a half-life of T1/2=742(13)ns. The state of interest was populated and spin-aligned via a single-neutron transfer on a highly enriched 98Mo target. A magnetic moment μexpt.=−0.627(20)μN was obtained. This result is far from the Schmidt value expected for a pure single-particle νh11/2 state. A comparison of experimental spectroscopic properties of this nucleus is made with results of multishell Interacting boson-fermion Model (IBFM-1) calculations. In this approach, the Jπ=11/2− isomeric state in 99Mo has a pure νh11/2 configuration. Its magnetic moment, as well as that of other two excited states could be reasonably well reproduced by reducing the free neutron spin g factor with a quenching factor of 0.45. This low value is not appropriate only for this case, similar values for the quenching factor being also required in order to describe magnetic moments in other nuclei from the same mass region

Time resolution measurements were performed using four digital timing algorithms and a pair of truncated-cone shaped, 38-mm diameter LaBr 3 (Ce) fast-timing scintillator detectors. The best resolution [FWHM=143(3) ps] was found for transitions from a 60Co source when fitting the rising part of sampled waveforms with a cubic polynomial and applying a leading-edge threshold. An average-pulse autocovariance function performed slightly worse [155(3) ps], but was found to be better than digital constant-fraction [178(4) ps] and leading-edge [177(4) ps] algorithms. Use of a 152Eu source allowed the performance of the four algorithms to be tested across a range of γ -ray energies with the LaBr 3 (Ce) detectors. Here the autocovariance algorithm performed best. Changing the sampling speed showed minimal degradation in the time resolution at 20 GS/s, though at 4 GS/s the resolutions were 30–60% worse. These results show that at sampling speeds of 20 or 40 GS/s the time resolutions obtained are close to those reported for analogue pulse-processing electronics. Compared to other works, using slower sampling speeds but higher vertical resolution, slightly worse performance was obtained.

International audience; Excited levels in Sr90, Sr92, Sr94, and Sr96 nuclei were reinvestigated using high-statistics multiple-γ coincidence data from neutron-induced fission of U235 and spontaneous fission of Cf252, measured using Exogam at Institut Laue Langevin and Gammasphere arrays, respectively. The experimental goal was the search for new excited levels and firm spin-parity assignments to known levels. A total of 23 new levels with 30 new or corrected decays and 39 new or improved spin-parity assignments were obtained in the four nuclei. Negative-parity structures on top of 3− excitation were firmly identified and extended to higher spins. New positive-parity structures in Sr94 and Sr96 were observed with 3+ excitations characteristic of γ collectivity. The 277.7-keV, E2 decay from the 1507.0-keV level to the second 0+ level in Sr96, found in this paper, completes the coexisting deformed band in this nucleus. To learn about the microscopic structure of levels in the Sr88−96 nuclei, we performed large-scale shell-model calculations. The calculations compared to the experiment, helped the discussion of the evolution of collectivity in strontium isotopes, highlighting the important role of various single-particle excitations in phase transitions and shape coexistence in the region. The special role of the neutron 9/2+[404] extruder as a catalyst of the deformation change in the region is highlighted.

A new analysis of the data from measurements of $\ensuremath{\gamma}$ radiation following spontaneous fission of $^{248}\mathrm{Cm}$ and $^{252}\mathrm{Cf}$, performed using the Eurogam2 and Gammashpere arrays, respectively, has revealed, for the first time, excited states in the neutron-rich nucleus $^{154}\mathrm{Ce}_{96}$. Using these fission data we have also improved uncertainties on $\ensuremath{\gamma}$-ray energies in the ground-state bands of several neutron-rich nuclei of the $\mathrm{A}\ensuremath{\approx}150$ mass region. The improved data provided precise systematics of the ${\mathrm{E}}_{\mathrm{exc}}({4}^{+})/{\mathrm{E}}_{\mathrm{exc}}({2}^{+})$ ratio in the region, which indicate that, in the Ce isotopic chain, the rigid-rotation limit is reached at the neutron number $N=96$, two neutrons ``later'' than in the chain of Nd isotopes. The new results suggest the involvement of the proton $9/{2}^{+}[404]$ extruder orbital in generating nuclear deformation in the $\mathrm{A}\ensuremath{\approx}150$ region, in addition to and analogous to the known role played by the neutron $11/{2}^{\ensuremath{-}}[505]$ extruder in this region. The catalytic-type action of both extruders is discussed.

Lifetimes of low- and high-spin states in the odd-A nucleus Hf-177 were measured during the EXILL&FATIMA campaign using a spectrometer equipped with eight HPGe-Clover detectors and 16 fast-timing LaBr3(Ce) detectors. For the determination of lifetimes in the pico- to nanosecond regime, the well-established generalized centroid difference method was used. Lifetimes of the 9/2(-), 9/2(+), 11/2(-), 11/2(+) states were remeasured, the lifetimes of the 13/2(-), 17/2(-), 13/2(+), 15/2(+), and 17/2(+) states were determined for the first time and an upper limit for the 19/2(+) state has been established. From these lifetimes absolute reduced transition probabilities were extracted and compared to particle-rotor-model calculations and quasiparticle-phonon-model calculations showing the importance of including multipole-multipole interactions in the description of odd-A nuclei in the rare earth region.

New ground-state level with spin-parity $1/{2}^{+}$ is established in $^{109}\mathrm{Mo}$, 69.8 keV below the previously reported $5/{2}^{+}$ ground state in this nucleus, based on precise spectroscopy measurements of $\ensuremath{\gamma}$ radiation following spontaneous fission of $^{248}\mathrm{Cm}$ performed using the Eurogam2 array of anti-Compton spectrometers. Analogous measurement of $\ensuremath{\gamma}$ radiation following spontaneous fission of $^{252}\mathrm{Cf}$, performed using the Gammasphere array, confirms the new $1/{2}^{+}$ ground state of $^{107}\mathrm{Mo}$, proposed recently and establishes the isomeric character of the $5/{2}^{+}$ first excited state in $^{107}\mathrm{Mo}$. Two $\ensuremath{\beta}$-decaying isomers are suggested in $^{111}\mathrm{Mo}$ nucleus based on regular energy systematics, supporting previous predictions. Low-energy excitations in Mo isotopes are interpreted and compared to calculations reported in the literature. The results suggest shape transition from prolate to oblate deformation at $N\ensuremath{\ge}67$.

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.

Background: Neutron-rich nuclei with mass number between 100 and 110 attract much attention, since several kinds of shapes, such as spherical, prolate, oblate, and triaxial shapes, are predicted. In particular, for neutron-rich Mo isotopes, different models predict different magnitudes and rigidity of triaxial deformation. Previous interpretations of experimental results based solely on low-lying 2+2 states are insufficient to distinguish between the rigid triaxial shape, γ vibration, or γ -soft rotor. Purpose: The shape evolution of 106Mo, 108Mo, and 110Mo is investigated through their 2+1-state lifetimes, decay-branching ratios of the 2+2 state, and energies of the low-lying collective excited states with Kπ = 0+, 2+, and 4+. Method: β -delayed γ -ray spectroscopy was employed for neutron-rich Nb and Zr isotopes produced at the RIKEN RI Beam Factory to populate excited states in 106Mo , 108Mo , and 110Mo . The EUroball-RIKEN Cluster Array was used for high-resolution γ -ray detection and lifetimes of the 2+1 states were determined using the UK fast-timing array of LaBr3(Ce) detectors. Results: New γ -ray transitions and levels are reported, including newly assigned 0+2 states in 108,110Mo . Quadrupole deformations were obtained for 106,108,110Mo from their 2+1 energies and lifetimes. The β -delayed neutron-emission probabilities of 108 Nb and 110 Nb were determined by examining the γ rays of their respective daughter decays. Conclusions: The even-odd energy staggering in the 2+2 band was compared with typical patterns of the γ -vibrational band, rigid triaxial rotor, and γ -soft rotor. The very small even-odd staggering of 106 Mo, 108Mo, and 110Mo favors a γ -vibrational band assignment. The kinematic moment of inertia for the 2+2 band showed a trend similar to the ground-state band, which is as expected for the γ -vibrational band. Beyond-mean-field calculations employing the constrained Hartree-Fock-Bogoliubov and local quasiparticle-random-phase approximation method using the SLy 5 + T interaction reproduced the ground and 2+2 bands in 106Mo and 108Mo . The collective wave functions are consistent with the interpretation of the 2+2 band as the γ -vibrational band of the prolate shape. However, the staggering pattern observed in 110Mo differs from the one suggested in the calculations which predict a γ -soft rotor. There was no experimental indication of the oblate shape or the γ -soft rotor predicted in these Mo isotopes.

International audience; The nature of the high-lying final levels of the 96Ygsβ decay, one of the three most important contributors to the high-energy reactor antineutrino spectrum, has been investigated in high-resolution γ-ray spectroscopy following the β decay as well as in a campaign of inelastic photon scattering experiments. The comprehensive approach establishes 1− levels associated with the Pygmy Dipole Resonance as high-lying final levels in the β decay. Branching ratios extracted from β decay complement photon scattering and allow the absolute E1 excitation strength to be determined for levels populated in both reactions. The combined data represents a comprehensive approach to the wavefunction of the 1− levels below the Qβ value, which are investigated in the Quasiparticle Phonon Model. The calculations reveal that the components populated in β decay contribute only with small amplitudes to the complex wavefunction of these 1− levels. A comparison of the β decay results to data from total absorption γ-ray spectroscopy demonstrates a good agreement between both measurements.

Excited states of the neutron-rich nucleus 148Ce have been populated by neutron-induced fission of 235U and 241Pu samples. Their electromagnetic decays were studied by means of γ-ray coincidence spectroscopy with fast-timing capabilities. Lifetimes of the 2+1 and 4+1 states of 148Ce were obtained and their E2 decay rates deduced. The B4=2 = B(E2; 4+1 → 2+1)=B(E2; 2+1 → 0+1) ratio indicates that 148Ce is a transitional nucleus while the N = 88/90 shape phase transition evolves into a gradual change of nuclear deformation for proton numbers Z < 60.

New results obtained in this work from measurements of $\ensuremath{\gamma}$ radiation following fission of $^{248}\mathrm{Cm}$ and $^{252}\mathrm{Cf}$, performed using Eurogam2 and Gammasphere arrays, respectively, reveal excitations corresponding to $\ensuremath{\gamma}$ vibrations and triaxial deformation present in $^{100}\mathrm{Zr}$ and $^{102}\mathrm{Zr}$ nuclei. This is the first observation of nonaxial bands in Zr isotopes. Such excitations probably occur due to competing prolate and oblate configurations, identified recently in these nuclei. Evolution of $\ensuremath{\gamma}$ softness and triaxiality in Zr isotopes is observed in the function of the neutron number.

${0}_{2}^{+}$ bands in $^{98}\mathrm{Sr}$ and $^{100}\mathrm{Zr}$, populated in spontaneous fission of $^{248}\mathrm{Cm}$ and $^{252}\mathrm{Cf}$, have been studied using the Eurogam2 and Gammasphere arrays. Phenomenological classification of excited ${0}^{+}$ levels in even-even nuclei of the $A\ensuremath{\approx}100$ region into four categories is presented and an interpretation for each category is proposed. Highly deformed ${0}_{1}^{+}$ ground states and low-energy ${0}_{2}^{+}$ levels in both nuclei are probably due to the 2p-2h excitation of two neutrons from the $9/{2}^{+}[404]$ extruder to the low-$\mathrm{\ensuremath{\Omega}}$ prolate and the $11/{2}^{\ensuremath{-}}[505]$ oblate orbitals originating from the ${h}_{11/2}$ shell, respectively. Candidates for ${0}^{+}, \ensuremath{\beta}$ vibrational states in $A\ensuremath{\approx}100$ region are suggested at $\mathrm{N}g60$.

Excited states in Sn-133 were investigated through the beta decay of In-133 at the ISOLDE facility. The ISOLDE Resonance Ionization Laser Ion Source (RILIS) provided isomer-selective ionization for In-133, allowing us to study separately, and in detail, the beta-decay branch of In-133 J(pi)= (9/2(+)) ground state and its J(pi) = (1/2(-)) isomer.Thanks to the large spin difference of the two beta-decaying states of In-133, it is possible to investigate separately the lower and higher spin states in the daughter, Sn-133, and thus to probe independently different single-particle and single-hole levels. We report here new gamma transitions observed in the decay of In-133, including those assigned to the deexcitation of the neutron-unbound states.

The gamma-ray decay of excited states of the one-valence-proton nucleus Sb-133 has been studied using cold-neutron induced fission of U-235 and Pu-241 targets, during the EXILL campaign at the ILL reactor in Grenoble. By using a highly efficient HPGe array, coincidences between gamma-rays prompt with the fission event and those delayed up to several tens of microseconds were investigated, allowing to observe, for the first time, high-spin excited states above the 16.6 mu s isomer. Lifetimes analysis, performed by fast-timing techniques with LaBr3(Ce) scintillators, revealed a difference of almost two orders of magnitude in B(M1) strength for transitions between positive-parity medium-spin yrast states. The data are interpreted by a newly developed microscopic model which takes into account couplings between core excitations (both collective and non-collective) of the doubly magic nucleus Sn-132 and the valence proton, using Skyrme effective interaction in a consistent way. The results point to a fast change in the nature of particle-core excitations with increasing spin. (C) 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license.

The nature of low-lying 3(-) levels in Nd-144 was investigated in the Nd-143(n, gamma gamma) cold neutron-capture reaction. The combination of the high neutron flux from the research reactor at the Institut Laue-Langevin and the high gamma-ray detection efficiency of the EXILL setup allowed the recording of gamma gamma coincidences. From the coincidence data precise branching ratios were extracted. Furthermore, the octagonal symmetry of the setup allowed angular-distribution measurements to determine multipole-mixing ratios. Additionally, in a second measurement the ultra-high resolution spectrometer GAMS6 was employed to conduct lifetime measurements using the gamma-ray induced Doppler-shift technique (GRID). The confirmed strong M1 component in the 3(3)(-) -> 3(1)(-) decay strongly supports the assignment of the 3(3)(-) level at 2779 keV as low-lying isovector octupole excitation. Microscopic calculations within the quasiparticle phonon model confirm an isovector component in the wave function of the 3(3)(-) level, firmly establishing this fundamental mode of nuclear excitation in near-spherical nuclei.

Lifetimes of intermediate-spin states in two rotational bands of 99Zr have been measured. These states were populated following the neutron-induced fission of 235U at the PF1B beamline of the Institut Laue-Langevin, Grenoble, during the EXILL-FATIMA campaign. The nucleus 99Zr59 exhibits shape coexistence and lies precisely on the border of an abrupt change in ground-state deformation when going from N=58 to N=60, making its study interesting for understanding the mechanisms involved in the rapid onset of deformation here. The B(E2) values extracted for decays in the ν3/2[541] band allow quadrupole deformations of β2=0.34(1) and 0.26(3) to be determined for the 821.6- and 1236.6-keV members, whereas β2=0.32(3) was found for the 850.5-keV member of the ν3/2[411]band. Some of the excited states known in 99Zr have been reasonably described with interacting boson-fermion model (IBFM) calculations. Type-II shell evolution is proposed to play a major role in modifying single-particle energies in 99Zr.

Exotic nuclei are characterized by a number of neutrons (or protons) in excess relative to stable nuclei. Their shell structure, which represents single-particle motion in a nucleus, may vary due to nuclear force and excess neutrons, in a phenomenon called shell evolution. This effect could be counterbalanced by collective modes causing deformations of the nuclear surface. Here, we study the interplay between shell evolution and shape deformation by focusing on the magnetic moment of an isomeric state of the neutron-rich nucleus 75Cu. We measure the magnetic moment using highly spin-controlled rare-isotope beams and achieving large spin alignment via a two-step reaction scheme that incorporates an angular-momentum-selecting nucleon removal. By combining our experiments with numerical simulations of many-fermion correlations, we find that the low-lying states in 75Cu are, to a large extent, of single-particle nature on top of a correlated 74Ni core. We elucidate the crucial role of shell evolution even in the presence of the collective mode, and within the same framework, we consider whether and how the double magicity of the 78Ni nucleus is restored, which is also of keen interest from the perspective of nucleosynthesis in explosive stellar processes., 10 pages, 4 figures

International audience; Excited states of the rubidium isotopes$_{37}^{87, 89, 91}$Rb have been studied at the INFN Legnaro National Laboratory. Measurements of the $\gamma$ -ray decay of fragments produced in binary grazing reactions resulting from the interaction of a beam of 530 MeV$^{96}$Zr ions with a$^{124}$Sn target have been complemented by studies of the $\gamma$ -ray decay of fission fragments produced in the interaction of a beam of 230 MeV$^{36}$S ions with a thick$^{176}$Yb target. The structure of the yrast states of$_{37}^{87, 89, 91}$Rb has been discussed within the context of spherical shell-model and cranked Nilsson-Strutinsky calculations.

9 pags., 8 figs., 4 tabs., The low-energy structure of Co65 was studied by means of γ-and fast-timing spectroscopy at the ISOLDE/CERN facility. The known level scheme of Co65 populated following the β-decay of Fe65 was expanded. The experimental results were compared with large-scale shell-model calculations. The measured long lifetime of the (1/21-) level confirms its nature as a highly collective state with proton excitations across the Z=28 gap and neutrons across the N=40 subshell., This work was partially supported by the Spanish MINECO through Projects No. FPA2014-57196 and No. FPA2015-65035-P and Centro de Excelencia Severo Ochoa Programme (Project No. SEV-2016-0597). Support by Grupo de Física Nuclear (GFN-UCM) and by the European Union Seventh Framework through ENSAR (Contract No. 262010) is also acknowledged. B.O. acknowledges funding by the CPAN project. S.R.L. acknowledges funding by the U.S. National Science Foundation under Contract No. PHY-07- 58100.

The main goal of this work is the determination of spins and parities of excited states in $^{97}\mathrm{Zr}$, among others the 2264.3-keV level, which had previously been tentatively reported as the $11/{2}^{\ensuremath{-}}$ excitation corresponding to the ${h}_{11/2}$ neutron orbital. Low-spin excited states in $^{97}\mathrm{Zr}$ were populated via the cold-neutron capture reaction. The $\ensuremath{\gamma}$ rays emitted following the reaction were measured using the highly efficient array of high-purity germanium detectors, EXILL, at the Institut-Laue-Langevin (ILL), Grenoble. The primary $\ensuremath{\gamma}$ rays deexciting the capture state in $^{97}\mathrm{Zr}$ were identified for the first time. The new, precise neutron binding energy in $^{97}\mathrm{Zr}$ of 5569.15(4) keV differs significantly from the value reported in the literature. The previously reported level scheme has been amended by several new low-spin levels. The ($n,\ensuremath{\gamma}$) data were complemented by a measurement of the ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of $^{97}\mathrm{Y}$ at the Lohengrin fission-fragment separator of the ILL, and the observation of the ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of $^{97}\mathrm{Y}$ populated in neutron-induced fission of $^{235}\mathrm{U}$ and measured using the EXILL Ge array. The combined data allowed unique spin-parity assignments for many levels in $^{97}\mathrm{Zr}$. The 2264.3-keV level, with a new spin-parity assignment of $9/{2}^{+}$, may correspond to the $\ensuremath{\nu}{g}_{9/2}$ extruder orbital.

Algebraic collective model (ACM) calculations for the even-even selenium isotopes $^{86,88}\mathrm{Se}$ have been performed to describe collective properties of these two transitional nuclei with only two and four valence neutrons, respectively. From the perspective of the ACM the nuclei turn out to be only weakly deformed, described by a very $\ensuremath{\gamma}$-soft potential. This is confirmed by Skyrme and Gogny energy density functional calculations. Additionally, the fully microscopic symmetry conserving configuration mixing method with the Gogny interaction has been applied to the study of these isotopes. The results show the transitional character of $^{86}\mathrm{Se}$ and the relevant role of the triaxial degree of freedom in the structure of these nuclei.

International audience; The Fission Product Prompt γ-ray Spectrometer (FIPPS) is a new instrument of the Institut Laue-Langevin (ILL) for the spectroscopy of nuclei produced after neutron induced reactions. The future upgrade of the instrument aims to explore the neutron-rich region of the nuclear chart with higher selectivity by identifying the fragments produced after neutron induced fission. The Gas-Filled-Magnet (GFM) technique has been chosen in order to obtain a good mass separation (50 msr and P/P > 10%). A GFM design consisting of a 1/r magnetic field index and Thales circle-shaped entrance and exit magnet edges is proposed. The characteristic of the magnet is presented with realistic magnetic field calculations and Monte-Carlo simulations.

International audience; Excited states in the neutron-rich nucleus 150Ba have been observed via β–γ spectroscopy at the Radioactive Isotope Beam Factory, RIKEN Nishina Center. The 150Ba ions were produced by the in-flight fission of a 238U beam with an energy of 345 MeV/nucleon. The E(2+) energy of 150Ba was identified at 100 keV, which is the lowest known in the neutron-rich Ba isotopes. A γ -ray peak was also observed at 597 keV. A mean-field calculation with a fully 3D real space was performed and a static octupole deformation was obtained for the Ba isotopes. Kπ = 0− and 1− excited states with significant octupole collectivity were newly predicted at around or lower than 1 MeV on the ground state of 150Ba by a random-phase approximation calculation. The 597 keV γ ray can be interpreted as a negative-parity state, showing that 150Ba may possess octupole collectivity.

Journal of physics / Conference Series Conference Series 1023, 012022 - (2018). doi:10.1088/1742-6596/1023/1/012022, Published by IOP Publ., Bristol

6 pags., 3 figs. -- Open Access funded by Creative Commons Atribution Licence 4.0. -- Presented at the XXXV Mazurian Lakes Conference on Physics, Piaski, Poland, September 3–9, 2017., Excited states in the neutron-rich isotope 133Sn were studied via the ß decay of 133In. Isomer selective ionization using the ISOLDE RILIS enabled the ß decays of 133Ings (I¿ = 9=2+) and 133mIn (II¿ = 1=2-) to be studied independently for the first time. A description of the experimental setup at the ISOLDE Decay Station is presented together with preliminary results from the experiment., This work was supported in part by the National Science Centre, Poland (NCN) under contracts No. UMO-2015/18/E/ST2/00217 and No. UMO- 2015/18/M/ST2/00523, by the Spanish MINECO via FPA2015-65035-P project and by the Portuguese FCT via CERN/FIS-NUC/0004/2015 project.

Delayed $\ensuremath{\gamma}$-ray and conversion-electron spectroscopy is performed on $A=152$ fission fragments, at the Lohengrin spectrometer of the Institut Laue-Langevin, providing a new decay scheme for $^{152}\mathrm{Pr}$. The quasiparticle phonon model, combined with the particle-rotor model, which allows octupole correlations and Coriolis mixing to be taken into account, is applied to analyze its low-energy structure. The main configurations are found to be $(\ensuremath{\pi}3/2[422]\ensuremath{\bigotimes}\ensuremath{\nu}5/2[642]){1}^{+}$ for the isomer and $(\ensuremath{\pi}3/2[541]\ensuremath{\bigotimes}\ensuremath{\nu}3/2[521]){3}^{+}$ for the ground state.

5 pags., 2 figs. -- Open Access funded by Creative Commons Atribution Licence 4.0. -- Presented at the XXXV Mazurian Lakes Conference on Physics, Piaski, Poland, September 3–9, 2017., The even–even nucleus 142Xe lies north-east of the doubly magic 132Sn on the neutron-rich side of the nuclear chart. In order to gain further information on the octupole collectivity and the evolution of quadrupole collectivity in this region, a “safe” Coulomb excitation experiment was carried out at the new HIE-ISOLDE facility (CERN) at the end of 2016. As the gamma-ray detector the Miniball spectrometer was used. Beam and target nuclei were detected using C-REX, i.e. an array of segmented Si detectors, covering forward as well as backward angles in the laboratory frame., This work is supported by the German Federal Ministry of Education and Research (BMBF) under contract 05P15RDCIA, by the EU under contract ENSAR 262010, by ISOLDE and the IS548-MINIBALL Collaboration.

Rapid shape changes are observed for neutron-rich nuclei with A around 100. In particular, a sudden onset of ground-state deformation is observed in the Zr and Sr isotopic chains at N = 60: Low-lying states in $N\ensuremath{\le}58$ nuclei are nearly spherical, while those with $N\ensuremath{\ge}60$ have a rotational character. Nuclear lifetimes as short as a few picoseconds can be measured using fast-timing techniques with ${\mathrm{LaBr}}_{3}$(Ce) scintillators, yielding a key ingredient in the systematic study of the shape evolution in this region. We used neutron-induced fission of $^{241}\mathrm{Pu}$ and $^{235}\mathrm{U}$ to study lifetimes of excited states in fission fragments in the $A\ensuremath{\sim}100$ region with the EXILL-FATIMA array located at the PF1B cold neutron beam line at the Institut Laue-Langevin. In particular, we applied the generalized centroid difference method to deduce lifetimes of low-lying states for the nuclei $^{98}\mathrm{Zr}$ (N = 58), $^{100}\mathrm{Zr}$, and $^{102}\mathrm{Zr}$ ($N\ensuremath{\ge}60$). The results are discussed in the context of the presumed phase transition in the Zr chain by comparing the experimental transition strengths with the theoretical calculations using the interacting boson model and the Monte Carlo shell model.

Excited states in $^{98}\mathrm{Y}$, populated in neutron-induced fission of $^{235}\mathrm{U}$ and in spontaneous fission of $^{248}\mathrm{Cm}$ and $^{252}\mathrm{Cf}$, have been studied by means of $\ensuremath{\gamma}$ spectroscopy using the Lohengrin fission-fragment separator at ILL Grenoble and the EXILL, Eurogam2, and Gammasphere Ge arrays. Two new isomers have been found in $^{98}\mathrm{Y}$: a deformed one with ${T}_{1/2}=180(7)$ ns and a rotational band on top of it, and a spherical one with ${T}_{1/2}=0.45(15)\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\text{s}$, analogous to the ${8}^{+}$ isomer in $^{96}\mathrm{Y}$, corresponding to the ${(\ensuremath{\nu}{g}_{7/2},\ensuremath{\pi}{g}_{9/2})}_{{8}^{+}}$ spherical configuration. Using the JYFLTRAP Penning trap, an accurate excitation energy of 465.7(7) keV has been determined for the 2.36-s isomer in $^{98}\mathrm{Y}$. This result and the studies of excited levels in $^{98}\mathrm{Zr}$, populated in ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of the isomer, indicate a new spin-parity, ${I}^{\ensuremath{\pi}}={(7)}^{+}$ for the isomer. The high spin and the decay properties of this isomer suggest the presence of the $9/{2}^{+}[404]$ neutron extruder orbital in its structure. This is consistent with the large deformation of the isomer, reported recently. The present work does not provide arguments to support the special role of the $\ensuremath{\nu}{g}_{7/2}\phantom{\rule{0.16em}{0ex}}\text{\ensuremath{-}}\phantom{\rule{0.16em}{0ex}}\ensuremath{\pi}{g}_{9/2}$ interaction (the spin-orbit-partner, or SOP, mechanism).

The existence of two close-lying nuclear states in ⁷³Ga has recently been experimentally determined: a 1/2⁻ spin-parity for the ground state was measured in a laser spectroscopy experiment, while a J_π = 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 ⁷³Ga populated in the β decay of ⁷³Zn produced at ISOLDE, CERN. Using β-gated, γ-ray singles, and γ –γ 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 ⁷³Ga have been measured using the fast-timing ;method with LaBr₃(Ce) detectors. From our study, we help clarify the excited structure of ⁷³G and we extend the existing ⁷³Zn decay to ⁷³Ga with 8 new energy levels and 35 γ transitions. We observe a 195-keV transition consistent with a γ ray de-exciting a short-lived state in the β-decay parent ⁷³Zn.

The (ν 5 2 [532] ⊗ 3 2 [411]) 4− state in 102Zr, populated in the β-decay of 102Y, has been measured to be isomeric with a mean lifetime of 9.5(7) ns. It decays via four transitions, two of which are ∆K = 2 (to the 3+ and 4+ members of the 2+ γ band) and one is ∆K = 4 (to the 4+ member of the ground state 0+ band). The fourth (low-energy) transition is inferred to decay to an as-yet unassigned state. Hindrances of 106 were derived for the ∆K = 2 transitions compared to Weisskopf estimates and the ∆K = 4 transition hindered by a factor of 109 . These values are consistent with the decay pattern of the analogous isomeric state in the neighbouring N = 62 nucleus 100Sr and with the broader systematics of such transitions. A comparison of the hindrances for the ∆K = 4 transitions suggests that 102Zr is hardened against the γ degree of freedom compared to 100Sr.

Lifetimes of low-lying yrast states in neutron-rich 94,96,98Sr have been measured by Germanium-gated γ−γ fast timing with LaBr3(Ce) detectors using the EXILL&FATIMA spectrometer at the Institut Laue-Langevin. Sr fission products were generated using cold-neutron-induced fission of 235U and stopped almost instantaneously within the thick target. The experimental B(E2) values are compared with results of Monte Carlo shell-model calculations made without truncation on the occupation numbers of the orbits spanned by eight proton and eight neutron orbits and show good agreement. Similarly to the Zr isotopes, the abrupt shape transition in the Sr isotopes near neutron number N=60 is identified as being caused by many-proton excitations to its g9/2 orbit.

International audience; The four-parameter algebraic collective model (ACM) Hamiltonian is used todescribe the nuclear structure of 88Se. It is shown that the ACM is capable of providinga reasonable description of the excitation energies and relative positions of the ground-stateband and band. The most probable interpretation of the nuclear structure of 88Se is that of atransitional nucleus. The Quasiparticle-plus-Phonon Model (QPM) was also applied to describethe nuclear motion in 88Se. Preliminarily calculations show that the collectivity of second excitedstate 2+2 is weak and that this state contains a strong two-quasiparticle component.

Only a small percentage of know nuclei has spherical symmetry, most of them are deformed. The problem of nuclear deformation was rst investigated in 1952 by the A.A. Bohr [1] who suggested that atomic nuclei can acquire shapes other than spherical through a process called spontaneous symmetry breaking (SSB). Because shapes of atomic nuclei largely depend on the interactions between nucleons, nuclear-deformation studies can provide valuable information on nuclear forces, including the so-called residual interactions, responsible for nuclear deformation. In case of octupole deformation, studied in this work, residual interactions correlate nucleons moving on orbits which dier by three units of angular momentum ( ` = 3), and have dierent parities. If the Fermi level of a nucleus is located between such levels octupole deformation may occur. This happens for aparticular numbers of protons and neutrons, called octupole magic numbers (N;Z = 34; 56; 88; 134). Because the wave functions describing octupole-deformed nuclei do not have well-dened parity in the intrinsic frame, in the laboratory frame one ob- serves specic pattern of excited states, called parity doublet. The aim of the present study was to reinvestigate the presence of octupole deformation in the 147La nucleus. The 147La nuclei were produced in spontaneous ssion of 252Cf and measured using the GAMMASPHERE array of Ge detectors. Taking as a starting point schemes proposed in previous works ([2] and [3]), a new scheme of excited states has been proposed for 147La, in which levels and transitions were arranged into a parity-doublet structure, thanks to newly observed transitions with energies 558.8, 436.5, 421.4 and 414.25 keV. In order to determine spins and parities of levels, angular correlation were analysed. Intensities of transitions allowed the determination of dipole moments and gyromagnetic coecients. The properties of excited levels in 147La, which are consistent with analogous properties observed in octupole-deformed nuclei around 147La, support octupole deformation in 147La.

International audience; FIPPS is the new nuclear physics instrument of ILL for the spectroscopy of nuclei produced in neutron-induced reactions. The performance of the first implementation of the setup will be shown, together with an overview of the first experimental campaign (December 2016-March 2017). Future perspectives and physics opportunities will then be discussed.

The half-life of the 15/2+ 1 state of the 3-valence-proton nucleus 135I has been measured to be 1.74(8) ns using the EXILL-FATIMA mixed array of Ge and LaBr3 detectors. The nuclei were produced following the cold neutron-induced fission of a 235U target at the PF1B beam line of the Institut Laue-Langevin. The extracted B(E2; 15/2+ → 11/2+) value enabled a test of seniority relations for the first time between E2 transition rates. Large-scale shell-model calculations were performed for 134Te and 135I, and reinterpreted in a single-orbit approach. The results show that the two-body component of the E2 operator can be large whereas energy shifts due to the three-body component of the effective interaction are small.

The decay of an isomeric state in the neutron-rich nucleus 129 Cd 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 238 U beam at the Radioactive Isotope Beam Factory at RIKEN. From the measured yields of γ -rays and internal conversion electrons, a multipolarity of E 3 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.

The management of rectal cancer relies on accurate MRI staging. Multi-modal treatments can downstage rectal cancer prior to surgery and may have an effect on MRI accuracy. We aim to correlate the findings of MRI staging of rectal cancer with histological analysis, the effect of neoadjuvant therapy on this and the implications of circumferential resection margin (CRM) positivity following neoadjuvant therapy. An analysis of histological data and radiological staging of all cases of rectal cancer in a single centre between 2006 and 2011 were conducted. Two hundred forty-one patients had histologically proved rectal cancer during the study period. One hundred eighty-two patients underwent resection. Median age was 66.6 years, and male to female ratio was 13:5. R1 resection rate was 11.1 %. MRI assessments of the circumferential resection margin in patients without neoadjuvant radiotherapy were 93.6 and 88.1 % in patients who underwent neoadjuvant radiotherapy. Eighteen patients had predicted positive margins following chemoradiotherapy, of which 38.9 % had an involved CRM on histological analysis. MRI assessment of the circumferential resection margin in rectal cancer is associated with high accuracy. Neoadjuvant chemoradiotherapy has a detrimental effect on this accuracy, although accuracy remains high. In the presence of persistently predicted positive margins, complete resection remains achievable but may necessitate a more radical approach to resection.

The first excited level of 96Mo was investigated in a high-statistics experiment using the 95Mo(n, γγ) cold neutron capture reaction. The measurements used the high cold neutron flux from the research reactor at Institut Laue-Langevin and employed the highly-efficient EXILL array to detect γ-ray coincidences. The recorded statistics allow identification of decay branches with only a small relative intensity including the E3 decay. With the knowledge of the newly measured branching ratio and the known transition probability, the lifetime of the level was determined and, subsequently, the strength of the other decay branches of the octupole phonon were calculated. The extracted electromagnetic decay strengths are compared to the systematics of the stable even–even molybdenum isotopes and values calculated in a Skyrme-force based quasiparticle random phase approximation and in a cluster approach. Additionally, the decay branch to the low-lying quadrupole isovector level was observed.

The CRIS setup at CERN-ISOLDE is a laser spectroscopy experiment dedicated to the high-resolution study of the spin, hyperfine structure and isotope shift of radioactive nuclei with low production rates (a few per second). It combines the Doppler-free resolution of the in-flight collinear geometry with the high detection efficiency of resonant ionisation. A recent commissioning campaign has demonstrated a 1% experimental efficiency, and as low as a 0.001% non-resonant ionisation. The current status of the experiment and its recent achievements with beams of francium isotopes are reported. The first identified systematic effects are discussed. publisher: Elsevier articletitle: The Collinear Resonance Ionization Spectroscopy (CRIS) experimental setup at CERN-ISOLDE journaltitle: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms articlelink: http://dx.doi.org/10.1016/j.nimb.2013.05.088 content_type: article copyright: Copyright © 2013 The Authors. Published by Elsevier B.V. ispartof: Nuclear Instruments & Methods in Physics Research B vol:317 issue:PART B pages:565-569 ispartof: location:Matsue, Japan status: published