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International audience; M4 resonances in light nuclei result from the p3/2 → d5/2 stretched excitations. Their configurations should be relatively simple, which makes them good benchmarks for the theoretical calculations taking into account the role of continuum couplings. The first experimental studies aiming at tracing the decay of the M4 stretched resonance in 13C, located at 21.47 MeV, were undertaken at the Cyclotron Centre Bronowice at the Institute of Nuclear Physics Polish Academy of Sciences in Kraków, Poland (IFJ PAN). They provided information on the proton and neutron decay channels of this resonance to 12B and 12C daughter nuclei, respectively. These experimental results were then compared with the theoretical calculations based on the Gamow Shell Model approach, in terms of energy, width, and in particular, the decay pattern. Furthermore, the studies of the next cases, namely, 14N and 16O, where several M4 resonances appear at around 20 MeV, have been recently performed at CCB. The new experimental findings will serve as a testing ground for future calculations describing the heavier nuclei in this important region of the nuclear chart.

The effective prompt response function full width at half maximum, PRF FWHM of 637 ps (obtained from the prompt gamma pairs of 477 keV and 700 keV associated with the yrast 2+ state in 206Po), and 1007 ps (obtained from the Compton gamma pairs of 189 keV and 237 keV associated with the 192Os(18O,16O)194Os 2 neutron transfer reaction) were used in fitting the time difference spectra obtained from the gamma coincident pairsof 206 keV and 374 keV in a symmetrised LaBr3(Ce) associated with the gamma transitions in 192Os, using the Half-life program. The values of half-life measured by fitting these PRF FWHM of 637 ps and 1007 ps separately show an excellent agreement of 282(16) ps and 272(21) ps, respectively, which correspond to the global half-life value of 282(4) ps for the 192Os. The mean value of 277(12) ps from these two measurements was used in calculating the B(E2; IL ->IL-2) of 4233(114) e2fm4, which is equivalent to be 81(19) W.u.

International audience; “Stretched” states are examples of the simplest nuclear excitations in the continuum, thus offering an excellent testing ground for various theoretical approaches. The decay of the stretched single-particle state in 13C, located at 21.47 MeV, was investigated in an experiment performed recently at the Cyclotron Centre Bronowice (CCB) at IFJ PAN in Kraków. First experimental information on the proton and neutron decay channels of this resonance was obtained by employing coincidence measurement of protons inelastically scattered on the 13C target and γ rays from daughter nuclei. The new experimental findings will be used for testing predictions obtained by the Gamow Shell Model calculations.

Fast-timing measurements at the focal plane of a separator can suffer from poor timing resolution. This is due to the variations in time-of-flight (ToF) for photons travelling to a given detector, which arise from the changes in the implantation positions of the recoil nuclei emitting the γ rays of interest. In order to minimise these effects on timing measurements, a procedure is presented that improves fast-timing data by performing ToF corrections on an event-by-event basis. This method was used to correct data collected with an array of eight LaBr 3 detectors, which detected γ rays from spatially distributed 138Gd recoil-implants at the focal plane of the Recoil-Ion-Transport-Unit (RITU) spectrometer. The Generalised Centroid Difference (GCD) method was used to extract a lifetime from data in conjunction with a new procedure to calibrate the time walk. The lifetime of the first 2 + state in 138Gd, populated by the decay of the K π = 8 − isomeric state, was measured to be 229(24) ps using the ToF-corrected data, which is consistent within three standard deviations to the literature value. The results together with Monte-Carlo simulations show that the ToF correction procedure reduced the uncertainty in the measured lifetimes by 3 % in the case of the spatially distributed nuclei at the focal plane of RITU. However, ∼ 12 % has been estimated for a similar experiment when using a larger focal plane i.e. the Super-FRS at the FAIR facility.

5 pags., 3 figs., 1 tab. -- Open Access funded by Creative Commons Atribution Licence 4.0, Gamow-Teller β decay is forbidden if the number of nodes in the radial wave functions of the initial and final states is different. This Δn=0 requirement plays a major role in the β decay of heavy neutron-rich nuclei, affecting the nucleosynthesis through the increased half-lives of nuclei on the astrophysical r-process pathway below both Z=50 (for N>82) and Z=82 (for N>126). The level of forbiddenness of the Δn=1ν1g →π0g transition has been investigated from the β decay of the ground state of Hg into the single-proton-hole nucleus Tl in an experiment at the ISOLDE Decay Station. From statistical observational limits on possible γ-ray transitions depopulating the π0g state in Tl, an upper limit of 3.9×10 % was obtained for the probability of this decay, corresponding to log⁡ft>8.8 within a 95% confidence limit. This is the most stringent test of the Δn=0 selection rule to date., Support from the European Union seventh framework through ENSAR contract no. 262010, the Science and Technology Facilities Council through grants ST/P005314/1, ST/L005743/1 and ST/J000051/1 (UK), the MINECO projects FPA2015-64969-P, FPA2015-65035-P and FPA2017-87568-P (Spain), FWO-Vlaanderen (Belgium), GOA/2015/010 (BOF KU Leuven), the Excellence of Science programme (EOS-FWO), and the Interuniversity Attraction Poles Programme initiated by the Belgian Science Policy Office (BriX network P7/12) is acknowledged. ZsP acknowledges support by the ExtreMe Matter Institute EMMI at the GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany. PHR and SMJ ac-knowledge support from the UK Department for Business, Energy and Industrial Strategy via the National Measurement Office.

This work is meant to respond the challenge of manufacturing osmium targets for nuclear astrophysics experiments using the activation method with alpha particles. In this context, PLD (Pulsed Laser Deposition) was used to prepare osmium targets without specks or wrinkles and with a very well defined and constant thickness. Characterization techniques as RBS (Rutherford Backscattering Spectrometry), AFM (Atomic Force Microscopy), SEM/EDX (Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy) and XRD (X-ray Diffraction) were used to determine accurately the features of the obtained targets. The obtained results reveal that the PLD technique is suitable for the preparation of high quality thin/thick osmium targets.

The structure of Po-208 populated through the EC/beta(+) decay of At-208 is investigated using gamma-ray spectroscopy at the ISOLDE Decay Station. The presented level scheme contains 27 new excited states and 43 new transitions, as well as a further 50 previously observed. rays which have been (re)assigned a position. The level scheme is compared to shell model calculations. Through this analysis approximately half of the beta-decay strength of At-208 is found to proceed via allowed decay and half via first-forbidden decay. The first-forbidden transitions predominantly populate core excited states at high excitation energies, which is qualitatively understood using shell model considerations. This mass region provides an excellent testing ground for the competition between allowed and first-forbidden beta-decay calculations, important for the detailed understanding of the nucleosynthesis of heavy elements.

ispartof: PHYSICAL REVIEW C vol:103 issue:4 status: published

International audience; Excited states in the mirror nuclei 31P and 31S were populated in the 1p and 1n exit channels of the reaction 20Ne + 12C, at a beam energy of 33 MeV. The 20Ne beam was delivered for the first time by the Piave-Alpi accelerator of the Laboratori Nazionali di Legnaro. Angular correlations of coincident γ-rays and Doppler-shift attenuation lifetime measurements were performed using the multi-detector array GASP in conjunction with the EUCLIDES charged particle detector. In the observed B(E1) strengths, the isoscalar component, amounting to 24% of the isovector one, provides strong evidence for breaking of the isospin symmetry in the A=31 mass region. Self-consistent beyond mean field calculations using Equation of Motion method based on a chiral potential and including two- and three-body forces reproduce well the experimental B(E1) strengths, reinforcing our conclusion. Coherent mixing from higher-lying states involving the Giant Isovector Monopole Resonance accounts well for the effect observed. The breaking of the isospin symmetry originates from the violation of the charge symmetry of the two- and three-body parts of the potential, only related to the Coulomb interaction.

Multinucleon transfer reactions in 90Zr+208Pb have been studied via fragment-γ coincidences, employing the PRISMA magnetic spectrometer coupled to the CLARA γ-array. An analysis on Y isotopes has been carried out incorporating spectroscopic as well as reaction mechanism aspects. New γ transitions have been observed in 94Y, confirming the findings of recent studies where nuclei were produced via fission of uranium, and a comparison with near-by 90,92Y isotopes populated in the same reaction has been discussed. Experimental cross sections have been extracted and compared with the GRAZING calculations, showing a fair agreement along the neutron pick-up side. The results confirm how multinucleon transfer reactions are a suitable mechanism for the study of neutron-rich nuclei.

International audience; Lifetimes of the low-energy levels in Nd136, populated in the reaction Te124(O16,4n), were measured with the ROSPHERE array at the Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH), Bucharest-Magurele. The data were analyzed using the recoil distance Doppler shift method, and, in the cases where lifetimes were τ⩽1 ps, Doppler attenuation effects were taken into account. The deduced electromagnetic transition probabilities are discussed in the framework of the five-dimensional collective Hamiltonian (5DCH) theoretical model implemented with the D1S Gogny force, and detailed systematics of several observables in the even-even Nd isotopic chain are presented that highlight the transitional character of the neutron-deficient Nd isotopes. The 5DCH predictions are in overall good agreement with the present experimental results.

An extended investigation of the low-spin structure of the Ni65 nucleus was performed at the Institut Laue-Langevin, Grenoble, France, via the neutron capture reaction Ni64(n,γ)Ni65, using the Fission Product Prompt Gamma-Ray Spectrometer High-Purity Ge array. The level scheme of Ni65 was significantly expanded, with two new levels and 87 newly found transitions. Angular correlation analyses were also performed, allowing us to assign spins and parities for a number of states and to determine multipolarity mixing ratios for selected γ transitions. The low-energy part of the experimental level scheme (up to about 1.4 MeV) was compared with Monte Carlo shell-model calculations, which predict spherical shapes for all states, apart from the 9/2+ and the second excited 1/2- states of oblate deformation., SCOPUS: ar.j, info:eu-repo/semantics/published

Medium and high spin states of the Y96 nucleus, located in the shape-coexistence region near Z=40 and N=60, were populated in thermal-neutron-induced fission of U233 and U235 targets, diluted in a scintillator. γ rays were measured with the FIssion Product Prompt γ-ray Spectrometer (FIPPS) high-purity germanium (HPGe) detector array, using double and triple γ-ray coincidence techniques and taking advantage of the efficient fission tag provided by the scintillating target material. A complex level scheme, extending up to 5.2 MeV and including excitations above the 8+β-decaying isomer, was investigated, and firm spin and parity assignments were given to a number of states, on the basis of angular correlation analysis and considerations on the γ-decay patterns. While the structures built on the 0− ground state and the 8+ isomer show irregular patterns typical for spherical shapes, the (6+) isomeric state at 1655 keV [with half-life of 181(9) ns], and the rotational band built on it [with spin-parity values between (6+) and (9+)], can be explained by Hartree-Fock-Bogoliubov calculations, if an oblate deformation is assumed. This is the first observation of a deformed structure in an N=57 isotone, lying three neutrons away from the N=60 line. An important finding is also the 115-keV transition which connects the (6+) 181(9)-ns isomer to the β-decaying 8+ spherical isomer, allowing us to firmly place the latter at 1541 keV excitation energy. This may be relevant for calculations of electron and antineutrino spectra from fission of actinides, for which Y96 is a prominent product.

The β decay of ^{208}Hg into the one-proton hole, one neutron-particle _{81}^{208}Tl_{127} nucleus was investigated at CERN-ISOLDE. Shell-model calculations describe well the level scheme deduced, validating the proton-neutron interactions used, with implications for the whole of the N>126, Z

The $^{86}\mathrm{Zr}$ nucleus, which has a low-lying level scheme characteristic of a transitional nucleus, presents, according to the existing electromagnetic transition data, a subunitary ${\mathrm{B}}_{4/2}=B(E2,{4}_{1}^{+}\ensuremath{\rightarrow}{2}_{1}^{+})/B(E2,{2}_{1}^{+}\ensuremath{\rightarrow}{0}_{1}^{+})$ ratio, which is anomalously low for a nonmagic nucleus, as it is outside the range of the traditional collective models values. In order to check this anomaly, we performed new measurements of the lifetimes of its low-lying states, with the $\ensuremath{\gamma}$-ray coincident recoil distance Doppler shift method, using the ROSPHERE detector array. New lifetimes were determined for the positive-parity yrast states up to the ${10}^{+}$ one, and for the ${8}_{2}^{+},\phantom{\rule{0.16em}{0ex}}{5}_{1}^{\ensuremath{-}}$, and ${7}_{1}^{\ensuremath{-}}$ states. The newly determined values of the $B(E2)$ values for the ${2}_{1}^{+}$ and ${4}_{1}^{+}$ states characterize a nucleus with a moderate quadrupole deformation and are well described by the interacting boson model. The ratio ${B}_{4/2}=1.38(22)$ is no longer anomalous. The low $B(E2)$ value of the ${6}_{1}^{+}$ state indicates a noncollective structure.

International audience; We report on the investigation of the shape coexistence phenomenon in the Ni isotopic chain, from A = 62 to A = 66, by using γ-ray spectroscopy techniques and different reaction mechanisms, such as sub-Coulomb barrier transfer reactions and thermal-neutron capture. Our aim is to understand, from the microscopic point of view, the appearance of nuclear deformation in Ni isotopes at low excitation energy. A series of experiments was performed at the Tandem Accelerator Laboratory in Bucharest, at ALTO IPN-Orsay and at the ILL reactor in Grenoble. Various mean-field theoretical approaches, as well as recent state-of-the-art Monte Carlo Shell Model (MCSM) calculations, predict in 66Ni a deep secondary prolate minimum in the nuclear potential energy surface at spin zero, resulting in a hindered electromagnetic decay towards the spherical ground state (i.e., with an E2 transition probability less than 1 W.u.). This has been confirmed in the first experiment performed in Bucharest. Less pronounced prolate minima, at higher excitation energies, are also expected in lighter neutron-rich Ni isotopes, from state-of-the-art Monte Carlo Shell Model (MCSM) calculations. Preliminary results are discussed for 62Ni and 64Ni, in comparison with theory predictions.

The β decay of 207Hg into the single-proton-hole nucleus 207Tl has been studied through γ-ray spectroscopy at the ISOLDE Decay Station (IDS) with the aim of identifying states resulting from coupling of the πs−11/2, πd−13/2, and πh−111/2 shell model orbitals to the collective octupole vibration. Twenty-two states were observed lying between 2.6 and 4.0 MeV, eleven of which were observed for the first time, and 78 new transitions were placed. Two octupole states (s1/2-coupled) are identified and three more states (d3/2-coupled) are tentatively assigned using spin-parity inferences, while further h11/2-coupled states may also have been observed for the first time. Comparisons are made with state-of-the-art large-scale shell model calculations and previous observations made in this region, and systematic underestimation of the energy of the octupole vibrational states is noted. We suggest that in order to resolve the difference in predicted energies for collective and noncollective t=1 states (t is the number of nucleons breaking the 208Pb core), the effect of t=2 mixing may be reduced for octupole-coupled states. The inclusion of mixing with t=0,2,3 excitations is necessary to replicate all t=1 state energies accurately.

This paper reports cross-section measurements of the ($n,{n}^{\ensuremath{'}}$) and ($p,{p}^{\ensuremath{'}}$) reactions on $^{16}\mathrm{O}$ and $^{28}\mathrm{Si}$ at Geel Electron Linear Accelerator and at the 9-MV Tandem Accelerator of Horia Hulubei National Institute for Physics and Nuclear Engineering, respectively. The main purpose was to measure the neutron- and proton-induced inelastic $\ensuremath{\gamma}$-production cross sections for all observed transitions in $^{16}\mathrm{O}$ and $^{28}\mathrm{Si}$, followed by the calculation of the corresponding total inelastic cross section. The results are compared with theoretical calculations performed using the talys 1.9 code, evaluated nuclear data, and previously reported experimental data. The broader goal of this work is to study whether and to what extent the neutron-induced inelastic cross sections of these nuclei can be inferred from those obtained using suitable charged particle reactions. We show that, by making use of the formal similarities between the neutron- and the proton-target optical model potentials and isospin symmetry in mirror nuclei, one can develop a procedure that combines experimental proton-induced inelastic cross sections with theoretical calculations to infer neutron inelastic cross sections. For $^{16}\mathrm{O}$ and $^{28}\mathrm{Si}$, the precision associated with this procedure is around 10--20% for most of the incident energy range.

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.

The level structure of La-130 has been investigated using the (121)sb(C-12, 3n) reaction with the ROSPHERE array at IFIN-HH, Bucharest. the level scheme was significantly extended with the observation of 45 new states and 100 new transitions. Several band structures have been identified and a clear connection with the lower-lying states has been established. A lifetime of tau = 3.6(2) ns has been measured for the 346-keV 6(-) state by the in-beam fast timing technique. the lifetimes of 18 high-spin states have been determined by applying the Doppler-shift attenuation method. the deformations derived from the experimental B(E2) transition strengths indicate distinct coexisting shapes at high spins in La-130. the experimental properties of both low- and high-spin states were compared with theoretical calculations performed in the frame of the two-quasiparticles-plus-rotor model. Two new negative-parity decoupled bands, with a deduced quadrupole deformation beta(2) = 0.150(15), were interpreted by coupling the proton in the 1/2[550] and 3/2[541] orbitals with the odd neutron occupying mainly the low-Omega orbitals from the d(3/2) and 5(1/2) states. A quadrupole deformation beta(2) = 0.220(17) was derived for a newly identified positive-parity decoupled band. This enhanced deformation was attributed to the involvement in the band configuration of the Omega = 1/2 (f(7/2), h(9/2)) intruder neutron orbital. the multiparticle configuration pi g(7/2)(h(11/2))(2) circle times nu (h(11/2)) was assigned to a high-spin negative-parity dipole band, based on the comparison of the experimental B(M1) transition strengths with values calculated by applying the geometrical model of Donau and Frauendorf., Ministry of Education and Research, Romania [PN-19-06-01-02], Authors are thankful to the FN Tandem staff of the Horia Hulubei National Institute of Physics and Nuclear Engineering for the good quality delivered beam. This work was supported by the Ministry of Education and Research, Romania, Contract No. PN-19-06-01-02.

6 pags., 6 figs. -- 27th International Nuclear Physics Conference (INPC2019) 29 July - 2 August 2019, Glasgow, UK, The neutron-deficient 115Cs was produced at ISOLDE, CERN by spallation reaction using 1.4 GeV proton on LaC2 target. The exotic decay modes were studied by using a charged particle array (DSSD and pad detectors) and a ¿-detector array (four Clovers) at the ISOLDE decay station (IDS). In this report, results on observed ß-delayed particle emission from 115Cs, a nucleus close to proton drip line, is presented. By measuring the time distribution in the delayed proton spectrum, the half-life of the ground state of 115Cs was extracted. The obtained half-life is in agreement with previous reported value. For the first time, the p-unbound states of 115Xe, obtained by measuring beta-delayed protons from 115Cs is reported., Ushasi Datta acknowledges with thanks to SERB, India for the financial support (travel) for attending and presenting the paper in the conference (INPC2019). Authors of SINP deeply acknowledge the SEND (XI th plan, DAE, India) and IENP/HENPP (XII th plan, DAE, India) project grant. This project has received funding from the European Union’s Horizon 2020 ENSAR2 project under grant agreement no 654002 and the Spanish research council under contract FPA2015-64969-P. The authors (P.Das and A.Bhattacharyya) acknowledge with thanks the financial support provided by the CSIR vide file number 09/489(0111)/2019EMR-I and 09/489(0115)/2019EMR-I respectively.

The present paper describes preparation and characterization of strontium targets for nuclear astrophysical experiments with alpha particles accelerated near the Gamow window energy. SrF2 and SrCO3 targets were obtained by thermal evaporation in similar conditions. Target characteristics (thickness, chemical purity and surface morphology) were determined via α transmission measurements, XRD and SEM/EDX analysis. The results reveal the SrF2 target exhibits better properties compared to the SrCO3 one for our nuclear astrophysics experiments. This result was supported by nuclear activation measurements with an α beam at the Bucharest Tandem 9 MV accelerator.

et al., In this paper the suitability of two non-destructive analytical techniques for identification of elemental signatures in samples containing uranium of different enrichments was studied. The measurements were based on particle induced X-ray emission (PIXE) and particle induced gamma-ray emission (PIGE) methods. The samples were irradiated by 3 and 5 MeV protons at the 3 MV Tandetron™ of Horia Hulubei National Institute for Physics and Nuclear Engineering. The characteristic X and gamma rays were measured using high purity germanium (HPGe) detectors. The GUPIX software was applied for processing the PIXE spectra, while a relative standardization was applied for PIGE analysis by using certified comparator standards and proton stopping powers calculated by SRIM.

The structure of $^{34}$Si was studied through $\gamma$ spectroscopy separately in the $\beta^-$ decays of $^{34}$Mg and $^{34}$Al at the ISOLDE facility of CERN. Different configurations in $^{34}$Si were populated independently from the two recently identified $\beta$-decaying states in $^{34}$Al having spin-parity assignments $J^\pi = 4^-$ dominated by the normal configuration $\pi (d_{5/2})^{-1} \otimes \nu (f_{7/2})$ and $J^\pi = 1^+$ by the intruder configuration $\pi (d_{5/2})^{-1} \otimes \nu (d_{3/2})^{-1}(f_{7/2})^{2}$. The paper reports on spectroscopic properties of $^{34}$Si such as an extended level scheme, spin and parity assignments based on log($ft$) values and $\gamma$-ray branching ratios, absolute $\beta$ feeding intensities and neutron emission probabilities. A total of 11 newly identified levels and 26 transitions were added to the previously known level scheme of $^{34}$Si. Large scale shell-model calculations using the {\sc sdpf-u-mix} interaction, able to treat higher order intruder configurations, are compared with the new results and conclusions are drawn concerning the predictive power of {\sc sdpf-u-mix}, the $N=20$ shell gap, the level of mixing between normal and intruder configurations for the 0$_1^+$, 0$_2^+$ and 2$_1^+$ states and the absence of triaxial deformation in $^{34}$Si.

Mean lifetimes of yrast states of the isotopes 174,176,178,180Hf have been measured using fast- electronic scintillation timing. Excited states of 74,176,178Hf were populated via β decay, while 180Hf was populated via Coulomb excitation. The lifetimes of the 2+ 1 and 4+ 1 states of all isotopes and the lifetimes of the 6+ 1 states of 174,178Hf were measured, using the slope and the centroid shift methods. The mean lifetime, τ (4+ 1 ) = 85(13) ps, of 178Hf has been determined for the first time. In addition, the mean lifetimes of the 2− 1 and the 3− 1 states of 176Hf have been determined. Systematic uncertainties on the evolution of data as a function of neutron number were reduced by using the same setup for all the isotopes of interest. The data are in agreement with other recent lifetime measurements where available and shows a shift of the maximum of collectivity for the Hf isotopic chain from neutron midshell at N = 104 to N = 100.

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.

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.

Lifetimes of yrast band states of \(^{174,176,178,180}\)Hf have been measured using fast-electronic scintillation timing or Coulomb excitation. The lifetimes of the \(2^+_1\), \(4^+_1\) states and apart from \(^{176}\)Hf also of the \(6^+_1\) states have been determined, using the slope and the centroid shift methods. By using the same setup for all isotopes of interest systematic uncertainties were reduced.

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.

Two-neutron transfer reactions serve as an important tool for nuclear-structure studies in the neutron-rich part of the nuclear chart. In this paper, we report on the first experimental attempt to populate the excited states of140 Ba employing the 2n-transfer reaction138 Ba(18 O,16 O)140 Ba. 140 Ba is highly important, as it is placed on the onset of octupole correlations and the lifetimes of its excited states are completely unknown, with the sole exception of the first state. The experiment was carried out at the Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN–HH) in Magurele, Romania. Lower limits on the lifetimes of the ground state band up to the state are reported. Furthermore, relative cross-sections regarding the 2n-transfer reaction with respect to the fusion and the total inelastic reaction channels have been deduced. Further investigation directions of the nuclear structure of 140 Ba are also discussed.

The ROmanian array for SPectroscopy in HEavy ion REactions (ROSPHERE) has been designed as a multi-detector setup dedicated to γ-ray spectroscopy studies at the Bucharest 9 MV Tandem accelerator. Consisting of up to 25 detectors (either Compton suppressed HPGe detectors or fast LaBr3(Ce) scintillator detectors) together with a state of the art plunger device, ROSPHERE is a powerful tool for lifetime measurements using the Recoil Distance Doppler Shift (RDDS) and the in-beam Fast Electronic Scintillation Timing (FEST) methods. The array's geometry, detectors, electronics and data acquisition system are described. Selected results from the first experimental campaigns are also presented.

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 neutron-rich 144,146 Ba isotopes have been studied recently in terms of their experimental B(E3) values [1,2]. Although featuring large uncertainties, the results were found to be significantly larger than any theoretical calculation. Similar questions exist for the slightly lighter isotope 140 Ba, which is particularly interesting since it is located at the onset of octupole correlations. The lifetimes of the lower-lying states are completely unknown, with the sole exception of the first 2 + state [3]. In this work, we report on the outcome of a short test run, attempting to populate the states of interest using the 138 Ba( 18 O, 16 O) 140 Ba reaction. The experiment was carried out at IFIN-HH using a specially manufactured nat Ba target sandwiched between two Au layers. This was considered imperative due to Barium's quick oxidation in air. Four beam energies (61,63,65,67 MeV) below the Coulomb barrier have been tested. The subsequent decay was measured using the Bucharest ROSPHERE array, consisting of 15 Ge detectors and 10 LaBr­ 3 (Ce) scintillators. The preliminary results from the test run report on the level population strengths and the limits in lifetime measurements, which are expected to provide new information on the structural effects in neutron-rich barium isotopes, especially regarding quadrupole and octupole degrees of freedom. The _ndings are also expected to act as stringent tests to theoretical modeling in this mass regime.

We report on the development of custom Front-End Electronics (FEE) dedicated to large area SiPM arrays for γ -ray spectroscopy applications in high counting rate conditions. Two types of commercially available 8 × 8 arrays of 6 × 6 mm 2 Silicon Photomultipliers (SiPM) and a quasi-circular array of 30 SiPM cells were coupled to dedicated Front End Electronics (FEE) boards and tested in combination with LaBr 3 (Ce) crystals. Energy resolution measurements were taken with standard calibration radioactive sources (60Co, 152Eu and 56 Co) while the timing response was studied in comparison with industry standard photomultiplier tubes . The energy resolution measured in this setup was down to 3.09(9)% at 661 keV, while the best timing resolution measured was 222.3(22) ps. Finally, the design of a SiPM based γ -ray detector, dedicated to fast-timing applications, is presented.

Target manufacturing is one fundamental issue in nuclear physics experiments using accelerators. A variety of targets are required, each having to satisfy specific conditions related to the experimental particularities. In this context, a brief description of the target preparation laboratory developed at IFIN-HH is presented in this paper. To fulfill the specific requirements, the laboratory is endowed with high performance equipment for evaporation-condensation (thermal resistance, e-based systems, sputtering) and cold rolling. During the last years, consistent technological improvements were achieved. Target characteristics, quality and reliability are important for our experiments’ feasibility in the first place, but also for the degree of confidence in the assumed accuracy. Consequently, XRD, AFM, SEM/EDX and RBS analyses are performed in collaboration with specialized departments from our institute and from other research centers.This paper is meant to synthetize our work so far.

A customizable and cost-efficient particle-detection system for transfer experiments at ROSPHERE has been designed and tested. Results from the commissioning experiment employing the 2 n -transfer reaction 94Zr(18O, 16O)96Zr are presented and discussed. The device allows for an efficient suppression of contributions from fusion-evaporation reactions and an improvement of the peak-to-background ratio by about one order of magnitude. The construction, characteristics, and performance are presented and further developments are outlined.

The C-12(alpha,gamma)O-16 reaction plays a central role in astrophysics, but its cross section at energies relevant for astrophysical applications is only poorly constrained by laboratory data. The reduced a width, gamma(11), of the bound 1(-) level in O-16 is particularly important to determine the cross section. The magnitude of gamma(11) is determined via sub-Coulomb a-transfer reactions or the beta-delayed a decay of N-16, but the latter approach is presently hampered by the lack of sufficiently precise data on the beta-decay branching ratios. Here we report improved branching ratios for the bound 1(-) level [b(beta,11) = (5.02 +/- 0.10) x 10(-2)] and for beta-delayed alpha emission [b(beta alpha) = (1.59 +/- 0.06) x 10(-5)]. Our value for b(beta alpha) is 33% larger than previously held, leading to a substantial increase in gamma(11). Our revised value for gamma(11) is in good agreement with the value obtained in a-transfer studies and the weighted average of the two gives a robust and precise determination of gamma(11), which provides significantly improved constraints on the C-12(alpha,gamma) cross section in the energy range relevant to hydrostatic He burning.

The electromagnetic decay properties of high spin states in 52Mn have been studied through various experiments with the GASP and EUROBALL arrays plus the ISIS charged-particle detector, the Neutron-Wall and the Recoil Filter Detector. From 7-7-particles coincidence measurements, spins and parities of these states have been determined and using the Doppler-shift attenuation method the mean life of some of these states have been determined. These results are compared with large scale shell-model calculations in the full fp shell.

International audience; A proton inelastic scattering experiment on a 57Fe target was performed at the 9 MV TANDEM facility of Horia Hulubei-National Institute of Physics and Nuclear Engineering, Bucharest-Măgurele, Romania. The purpose was to determine the γ-production cross sections of the transitions observed in the 57Fe(p, p’γ)57Fe reaction. The detection system consisted of 4 HPGe detectors for detection and a Faraday cup for beam integration. The proton energy was varied from 5 to 16 MeV, in 1-MeV steps. In the current analysis, experimental cross sections were determined only for the high-volume detectors, placed at 110◦ and 150◦ with respect to the beam axis. This work presents the data analysis procedure and the preliminary experimental cross sections for the most intense transitions decaying from the first seven excited states in 57Fe. The results are compared with TALYS 1.9 theoretical calculations performed using default input parameters.

Lifetimes of several short-lived excited states in Nd138 were measured with the ROSPHERE array at IFIN-HH, Bucharest, using the recoil-distance Doppler shift technique following the Sb123(F19,4n) reaction. The resulting electromagnetic transition probabilities are compared to large-scale shell model calculations and to constrained Hartree-Fock-Bogoliubov calculations with the Gogny D1S interaction, configuration mixing, and a five-dimensional collective Hamiltonian formalism. The onset of collectivity in Nd isotopes below the N=82 shell closure and the deformation induced by the alignment of protons and neutron holes in the h11/2 orbitals are discussed.