Search

The low-lying excited states in the neutron-deficient $N = Z + 1$ nucleus $^{87}_{43}$Tc$_{44}$ have been studied via the fusion-evaporation reaction $^{54}$Fe $(^{36}Ar, 2n1p)$ $^{87}$Tc at the Grand Accelerateur National d'Ions Lourds (GANIL), France. The AGATA spectrometer was used in conjunction with the auxiliary NEDA, Neutron Wall, and DIAMANT detector arrays to measure coincident prompt γ rays, neutrons, and charged particles emitted in the reaction. A level scheme of $^{87}$Tc from the $(9/2^+_{g.s})$ state to the $( 33 / 2^+_1$) state was established based on six mutually coincident γ -ray transitions. The constructed level structure exhibits a rotational behavior with a sharp backbending at $ℏω ≈ 0.50$ MeV. A decrease in alignment frequency and increase in alignment sharpness in the odd-mass isotonic chains around $N=44$ is proposed as an effect of the enhanced isoscalar neutron-proton interactions in odd-mass nuclei when approaching the $N=Z$ line.

Background: Shell hydrogen burning during the asymptotic giant branch (AGB) phase through the oxygen isotopes has been indicated as a key process that is needed to understand the observed O 18 / O 16 relative abundance in presolar grains and in stellar atmospheres. This ratio is strongly influenced by the relative strengths of the reactions O 18 ( p , α ) N 15 and O 18 ( p , γ ) F 19 in low-mass AGB stars. While the former channel has been the focus of a large number of measurements, the ( p , γ ) reaction path has only recently received some attention and its stellar reaction rate over a wide temperature range rests on only one measurement. Purpose: Our aim is the direct measurement of states in F 19 as populated through the reaction O 18 ( p , γ ) F 19 to better determine their influence on the astrophysical reaction rate, and more generally to improve the understanding of the nuclear structure of F 19 .Method: Branchings and resonance strengths were measured in the proton energy range E p lab = 150 – 400 keV , using a high-purity germanium detector inside a massive lead shield. The measurement took place in the ultra-low-background environment of the Laboratory for Underground Nuclear Astrophysics (LUNA) experiment at the Gran Sasso National Laboratory, leading to a highly increased sensitivity. Results: The uncertainty of the γ branchings and strengths was improved for all four resonances in the studied energy range; many new transitions were observed in the case of the 334 keV resonance, and individual γ decays of the 215 keV resonance were measured for the first time. In addition a number of transitions to intermediate states that decay through α emission were identified. The strengths of the observed resonances are generally in agreement with literature values. Conclusions: Our measurements substantially confirm previous determinations of the relevant resonance strengths. Therefore the O 18 ( p , γ ) F 19 reaction rate does not change with respect to the reaction rate reported in the compilations commonly adopted in the extant computations of red-giant branch and AGB stellar models. Nevertheless, our measurements definitely exclude a nonstandard scenario for the fluorine nucleosynthesis and a nuclear physics solution for the O 18 depletion observed in Group 2 oxygen-rich stardust grains.

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

The electromagnetic structure of Zn66 at low excitation energy was investigated via low-energy Coulomb excitation at INFN Legnaro National Laboratories, using the Gamma Array of Legnaro Infn Laboratories for nuclEar spectrOscopy (GALILEO) γ-ray spectrometer coupled to the SPIDER (Silicon PIe DEtectoR). A set of reduced E2, E3, and M1 matrix elements was extracted from the collected data using the gosia code, yielding 12 reduced transition probabilities between the low-spin states and the spectroscopic quadrupole moment of the 21+ state. The B(E2) values for transitions depopulating the 02+ state have been determined for the first time, allowing for the lifetime of this state to be deduced and, consequently, the ρ2(E0;02+→01+) monopole transition strength to be extracted. In addition, the B(E3;31−→01+) value has been determined for the first time in a Coulomb excitation experiment. The obtained results resolve the existing discrepancies between literature lifetimes and demonstrate that Zn66 cannot be described by using simple collective models. Therefore, new state-of-the-art beyond-mean-field and large-scale shell-model calculations were performed in order to interpret the structure of this nucleus. Both the experimental and theoretical results suggest that the triaxial degree of freedom has an important impact on electromagnetic properties of Zn66, while the unique features of the 02+ state indicate its distinct and rather isolated structure.

To test the predictive power of ab initio nuclear structure theory, the lifetime of the second 2(+) state in neutron-rich O-20, tau(2(2)(+)) = 150(-30)(+80) fs, and an estimate for the lifetime of ...

The g factor of the $$12^+$$ K-isomer in $$^{174}$$ W has been measured by means of the time-differential perturbed angular distribution technique as $$g(12^+)=+0.304(11)$$ . In addition, the half-life of the isomer has been remeasured as $$T_{1/2}(12^+)=124(8)$$ ns, in agreement with the literature value and confirming the anomalous hindrance F of the E2 transition to the $$10^+$$ level of the ground state band with respect to the $$\gamma $$ -tunnelling model prediction. The measured g factor has been compared with estimates based on experimental g factors from odd-mass isotopes in the same mass region and with Nilsson model calculations. The results establish unique features of the $$12^+$$ K-isomer in $$^{174}$$ W, which can possess a non-pure intrinsic configuration and/or can be characterised by values of the intrinsic quadrupole moment $$Q_0$$ and the rotational g factor $$g_R$$ significantly different with respect to the majority of K-isomers at mass $$A \approx 180$$ .

6 pags., 4 figs., The γ-ray emission from the nuclei Fe following Coulomb excitation at bombarding energy of 400-440 AMeV was measured with special focus on E1 transitions in the energy region 4-8 MeV. The unstable neutron-rich nuclei Fe were produced at the FAIR-GSI laboratories and selected with the FRS spectrometer. The γ decay was detected with AGATA. From the measured γ-ray spectra the summed E1 strength is extracted and compared to microscopic quasi-particle phonon model calculations. The trend of the E1 strength with increasing neutron number is found to be fairly well reproduced with calculations that assume a rather complex structure of the 1 states (three-phonon states) inducing a strong fragmentation of the E1 nuclear response below the neutron binding energy., This work was partially supported by INFN (Italy) and STFC (UK), the Swedish Research Council (Vetenskapsrådet, VR 2010-147, 2011-5253, and 2016-3969), BMBF NuSTAR-AGATA 05P18RDFN9 and BMBF NuSTAR 05P18RDFN1. The project was co-funded by the European Commission under the 7th Framework Program for RTD (2007-2013) under the Capacities Program (Contract Number 262010, ENSAR). This work was par-tially supported by the Ministry of Science, and Generalitat Valenciana, Spain, under the Grants SEV-2014-0398, FPA2017-84756-C4, PROMETEO/2019/005 and by the EU FEDER funds.

The lifetimes of the low-lying excited states 2(+) and 4(+) have been directly measured in the neutron-deficient Sn-106,Sn-108 isotopes. the nuclei were populated via a deep-inelastic reaction and the lifetime measurement was performed employing a differential plunger device. the emitted gamma rays were detected by the AGATA array, while the reaction products were uniquely identified by the VAMOS++ magnetic spectrometer. Large-Scale Shell-Model calculations with realistic forces indicate that, independently of the pairing content of the interaction, the quadrupole force is dominant in the B(E2; 2(1)(+) -> 0(g.s)(+)) values and it describes well the experimental pattern for Sn104-114 ; the B(E2;(+)(4) -> 2(1)(+)) values, measured here for the first time, depend critically on a delicate pairing-quadrupole balance, disclosed by the very precise results in Sn-108. (C) 2020 the Authors. Published by Elsevier B.V., European Union's Seventh Framework Programme for Research and Technological DevelopmentEuropean Union (EU) [262010]; Fondazione Cassa di Risparmio Padova e Rovigo under the project CONPHYT, starting grant in 2017; Swedish Research CouncilSwedish Research Council [822-2005-3332, 821-2010-6024, 821-2013-2304, 621-20145558, 2017-0065]; Knut and Alice Wallenberg FoundationKnut & Alice Wallenberg Foundation [2005.0184]; Scientific and Technological Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [114F473]; Ministerio de Ciencia e InnovacionInstituto de Salud Carlos IIISpanish Government [SEV-2014-0398, FPA2017-84756-C4, EEBBI-15-09671]; Generalitat ValencianaGeneralitat Valenciana [PROMETEO/2019/005]; EU-FEDER fundsEuropean Union (EU); Croatian Science Foundation [7194]; Hungarian National Research and Innovation Office (NKFIH) [K128947, PD124717, GINOP-2.3.3-15-2016-00034]; Polish National Science Centre under the COPIN-IN2P3 project [2014-14-M-ST2-00738, 2016-22M-ST2-00269, 2017-25-B-ST2-01569]; Polish National Science Centre under the COPIGAL project [2014-14-M-ST2-00738, 2016-22M-ST2-00269, 2017-25-B-ST2-01569]; Polish National Science Centre under the POLITA project [2014-14-M-ST2-00738, 2016-22M-ST2-00269, 2017-25-B-ST2-01569], The authors would like to thank the AGATA and VAMOS collaborations. Special thanks go to the GANIL technical staff for their help in setting up the apparatuses and the good quality beam and to A. Poves for his fruitful comments. This work was partially supported by the European Union's Seventh Framework Programme for Research and Technological Development (grant no. 262010). A.G. acknowledges the support of the Fondazione Cassa di Risparmio Padova e Rovigo under the project CONPHYT, starting grant in 2017. the work was also supported (B.C, H.L., J.N. and U.J.) by Swedish Research Council under the grant agreements nos. 822-2005-3332, 821-2010-6024, 821-2013-2304, 621-20145558 and 2017-0065, and by the Knut and Alice Wallenberg Foundation grant no. 2005.0184, (B.S.) by the Scientific and Technological Council of Turkey (TUBITAK) under the project no. 114F473, (A.G., A.J. and R.P.) by the Ministerio de Ciencia e Innovacion under the contracts nos. SEV-2014-0398, FPA2017-84756-C4 and EEBBI-15-09671, by the Generalitat Valenciana under the grant agreement no. PROMETEO/2019/005 and by the EU-FEDER funds, (T.M and S.S.) by the Croatian Science Foundation under the project no. 7194, (I.K and D.S.) by the Hungarian National Research and Innovation Office (NKFIH) under the project nos. K128947, PD124717 and GINOP-2.3.3-15-2016-00034, (M.P.) by the Polish National Science Centre with the grants nos. 2014-14-M-ST2-00738, 2016-22M-ST2-00269 and 2017-25-B-ST2-01569 under the COPIN-IN2P3, COPIGAL and POLITA projects.

The transitional nuclei $^{134}$Ba and $^{133}$Ba are investigated after multinucleon transfer employing the high-resolution Advanced GAmma Tracking Array coupled to the magnetic spectrometer PRISMA at the Laboratori Nazionali di Legnaro, Italy, and after fusion-evaporation reaction at the FN tandem accelerator of the University of Cologne, Germany. The Jπ=19/2+ state at 1942 keV in $^{133}$Ba is identified as an isomer with a half-life of 66.6(20)ns corresponding to a B(E1) value of 7.7(4)×10−6e2fm2 for the Jπ=19/2+ to Jπ=19/2− transition. The level scheme of $^{134}$Ba above the Jπ=10+ isomer is extended to approximately 6 MeV. A pronounced backbending is observed at ℏω=0.38 MeV along the positive-parity yrast band. The results are compared to the high-spin systematics of the Z=56 isotopes. Large-scale shell-model calculations employing the GCN50:82, SN100PN, SNV, PQM130, Realistic SM, and EPQQM interactions reproduce the experimental findings and elucidate the structure of the high-spin states. The shell-model calculations employing the GCN50:82 and PQM130 interactions reproduce alignment properties and provide detailed insight into the microscopic origin of this phenomenon in transitional $^{134}$Ba.

Background: Levels fulfilling the seniority scheme and relevant isomers are commonly observed features in semimagic nuclei; for example, in Sn isotopes (Z=50). Seniority isomers in Sn, with dominantly pure neutron configurations, directly probe the underlying neutron-neutron (νν) interaction. Furthermore, an addition of a valence proton particle or hole, through neutron-proton (νπ) interaction, affects the neutron seniority as well as the angular momentum. Purpose: Benchmark the reproducibility of the experimental observables, like the excitation energies (EX) and the reduced electric-quadrupole transition probabilities [B(E2)], with the results obtained from shell-model interactions for neutron-rich Sn and Sb isotopes with N

The high-spin structures of 136Ba and 137Ba are investigated after multinucleon-transfer (MNT) and fusion-evaporation reactions. 136Ba is populated in a 136Xe+238U MNT reaction employing the high-resolution Advanced GAmma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA at the Laboratori Nazionali di Legnaro, Italy, and in two 9Be + 130Te fusion-evaporation reactions using the High-efficiency Observatory for -Ray Unique Spectroscopy (HORUS) at the FN tandem accelerator of the University of Cologne, Germany. Furthermore, both isotopes are populated in an elusive reaction channel in the 11B+130Te fusion-evaporation reaction utilizing the HORUS -ray array. The level scheme above the J� = 10+ isomer in 136Ba is revised and extended up to an excitation energy of approx. 5.5 MeV. From the results of angular-correlation measurements, the Ex = 3707- and Ex = 4920-keV states are identified as the bandheads of positive- and negative-parity cascades. While the high-spin regimes of both 132Te and 134Xe are characterized by high-energy 12+ ! 10+ transitions, the 136Ba E2 ground-state band is interrupted by negativeparity states only a few hundred keV above the J� = 10+ isomer. Furthermore, spins are established for several hitherto unassigned high-spin states in 137Ba. The new results close a gap along the highspin structure of N < 82 Ba isotopes. Experimental results are compared to large-scale shell-model calculations employing the GCN50:82, Realistic SM, PQM130 and SN100PN interactions. The calculations suggest that the bandheads of the positive-parity bands in both isotopes are predominantly of proton character.

Lifetime measurements of excited states of the light N = 52 isotones 88 Kr , 86 Se , and 84 Ge have been performed, using the recoil distance Doppler shift method and VAMOS and AGATA spectrometers for particle identification and gamma spectroscopy, respectively. The reduced electric quadrupole transition probabilities B ( E 2 ; 2 + → 0 + ) and B ( E 2 ; 4 + → 2 + ) were obtained for the first time for the hard-to-reach 84 Ge . While the B ( E 2 ; 2 + → 0 + ) values of 88 Kr , 86 Se saturate the maximum quadrupole collectivity offered by the natural valence ( 3 s , 2 d , 1 g 7 / 2 , 1 h 11 / 2 ) space of an inert 78 Ni core, the value obtained for 84 Ge largely exceeds it, suggesting that shape coexistence phenomena, previously reported at N ≲ 49 , extend beyond N = 50 . The onset of collectivity at Z = 32 is understood as due to a pseudo-SU(3) organization of the proton single-particle sequence reflecting a clear manifestation of pseudospin symmetry. It is realized that the latter provides actually reliable guidance for understanding the observed proton and neutron single particle structure in the whole medium-mass region, from Ni to Sn, pointing towards the important role of the isovector-vector ρ field in shell-structure evolution.

A Coulomb-excitation experiment to study electromagnetic properties of Ca42 was performed using a 170-MeV calcium beam from the TANDEM XPU facility at INFN Laboratori Nazionali di Legnaro. γ rays from excited states in Ca42 were measured with the AGATA spectrometer. The magnitudes and relative signs of ten E2 matrix elements coupling six low-lying states in Ca42, including the diagonal E2 matrix elements of 21+ and 22+ states, were determined using the least-squares code gosia. The obtained set of reduced E2 matrix elements was analyzed using the quadrupole sum rule method and yielded overall quadrupole deformation for 01,2+ and 21,2+ states, as well as triaxiality for 01,2+ states, establishing the coexistence of a weakly deformed ground-state band and highly deformed slightly triaxial sideband in Ca42. The experimental results were compared with the state-of-the-art large-scale shell-model and beyond-mean-field calculations, which reproduce well the general picture of shape coexistence in Ca42.

International audience; Isomeric states in isotopes in the vicinity of doubly-magic 208Pb were populatedfollowing reactions of a relativistic 208Pb primary beam impinging on a9Be fragmentation target. Secondary beams of 198,200,202,206Pb and 206Hg wereisotopically separated and implanted in a passive stopper positioned in thefocal plane of the GSI Fragment Separator. Delayed γ rays were detected withthe Advanced Gamma Tracking Array (AGATA). Decay schemes were reevaluatedand interpreted with shell-model calculations. The momentumdependentpopulation of isomeric states in the two-nucleon hole nuclei206Pb/206Hg was found to differ from the population of multi neutron-holeisomeric states in 198,200,202Pb.

Background: While the $N=50$ shell-gap evolution towards $^{78}\mathrm{Ni}$ is presently in the focus of nuclear structure research, experimental information on the neutron effective single-particle energy sequence above the $^{78}\mathrm{Ni}$ core remain scarce. Direct nucleon-exchange reactions are indeed difficult with presently available post-accelerated radioactive-ion beams (especially for high orbital-momentum orbitals) in this exotic region.Purpose: In this study we probe the evolution of the $\ensuremath{\nu}1{g}_{7/2}$ effective single-particle energy which is a key to understanding the possible evolution of the spin-orbit splitting due to the proton-neutron interaction in the $^{78}\mathrm{Ni}$ region. To achieve this goal, a method based on lifetime measurements is used for the first time. The obtained lifetimes of the $7/{2}_{1}^{+}$ states in $^{87}\mathrm{Kr}$ and $^{85}\mathrm{Se}$ are used to investigate the $\ensuremath{\nu}1{g}_{7/2}$ evolution.Method: Yrast and near-yrast states in the light $N=51$ isotones $^{85}\mathrm{Se}$ and $^{87}\mathrm{Kr}$ were populated via multinucleon transfer reactions, using a $^{82}\mathrm{Se}$ beam and a $^{238}\mathrm{U}$ target at the LNL tandem-ALPI facility. The prompt $\ensuremath{\gamma}$ rays were detected by the AGATA Demonstrator and particle identification was performed using the PRISMA spectrometer. Lifetime measurements were performed by using the Cologne plunger device for deep inelastic reactions and the Recoil Distance Doppler Shift technique.Results: We obtain ${\ensuremath{\tau}}_{(7/{2}_{1}^{+})}=0.{4}_{\ensuremath{-}0.4}^{+1.6}$ ps for $^{87}\mathrm{Kr}$. In the case of $^{85}\mathrm{Se}$ an upper limit of 3(2) ps is obtained for the ${\ensuremath{\tau}}_{7/{2}_{1}^{+}}$ value.Conclusion: For $^{87}\mathrm{Kr}$, the measured $(7/{2}_{1}^{+})$ lifetime is consistent with a core-coupled ${2}^{+}\ensuremath{\bigotimes}\ensuremath{\nu}2{d}_{5/2}$ configuration for this state. This result is consistent with that obtained by direct reaction, which validates our method. For $^{85}\mathrm{Se}$, the measured $7/{2}_{1}^{+}$ lifetime limit indicates a very small contribution of the $\ensuremath{\nu}1{g}_{7/2}$ configuration to the wave function of this state.

The structure of the S33 nucleus was investigated in the Mg24(N14,αp) fusion-evaporation reaction using a 40-MeV N14 beam. The level scheme was extended up to an excitation energy of 11.7 MeV and spin 19/2+. Lifetimes of the intermediate- and high-spin states have been investigated by the Doppler shift attenuation method. Data were compared with different shell-model calculations where effective interactions involving two main shells, the sd and the fp, are used.

Prompt γ-ray spectroscopy of the neutron-rich $^{96}$Kr, produced in transfer- and fusion-induced fission reactions, has been performed using the combination of the Advanced Gamma Tracking Array and the VAMOS++ spectrometer. A second excited state, assigned to $J^π$ = $4^+$, is observed for the first time, and a previously reported level energy of the first 2+ excited state is confirmed. The measured energy ratio R4/2 = E($4^+$)/E($2^+$) = 2.12(1) indicates that this nucleus does not show a well-developed collectivity contrary to that seen in heavier N = 60 isotones. This new measurement highlights an abrupt transition of the degree of collectivity as a function of the proton number at Z = 36, of similar amplitude to that observed at N = 60 at higher Z values. A possible reason for this abrupt transition could be related to the insufficient proton excitations in the g9/2, d5/2, and s1/2 orbitals to generate strong quadrupole correlations or to the coexistence of competing different shapes. An unexpected continuous decrease of R4/2 as a function of the neutron number up to N = 60 is also evidenced. This measurement establishes the Kr isotopic chain as the low-Z boundary of the island of deformation for N = 60 isotones. A comparison with available theoretical predictions using different beyond mean-field approaches shows that these models fail to reproduce the abrupt transitions at N = 60 and Z = 36.

For the first time the astrophysical factor of the $^{10}\mathrm{B}(p,{\ensuremath{\alpha}}_{0})^{7}\mathrm{Be}$ reaction has been measured over a wide energy range, from 5 keV to 1.5 MeV, via the Trojan horse method (THM) applied to the quasifree $^{2}\mathrm{H}(^{10}\mathrm{B},\ensuremath{\alpha}^{7}\mathrm{Be})n$ reaction. Therefore, the $S(E)$ factor has been recast into absolute units by scaling in the energy range 200 keV--1.2 MeV to a recent measurement using the activation method, leading to a normalization uncertainty of $4%$. An $R$-matrix fit of the THM data was performed, to parametrize the $S$ factor, obtain spectroscopic information on the populated resonances, and compare with other recent experiments. Finally, a new determination of the screening potential ${U}_{e}$ has been obtained, ${U}_{e}=240\ifmmode\pm\else\textpm\fi{}50$ eV, with a much smaller error than our previous measurement.

International audience; A new segmented particle detector, SPIDER, has been designed to be used as an ancillary device with the GALILEO γ-ray spectrometer, as well as with other multi-detector γ-ray arrays that will be available at LNL in the future (e.g. AGATA). To commission the SPIDER-GALILEO experimental setup, a multi-step Coulomb excitation experiment was carried out with a 240 MeV beam of (66)Zn produced by the Tandem-XTU accelerator at INFN Laboratori Nazionali di Legnaro. The measured particle and γ-ray spectra are compared with the results of detailed GEANT4 simulations which used the Coulomb excitation cross sections, estimated with the computer code GOSIA, as an input. The preliminary results indicate that precise transition probabilities will be obtained which are essential for solving discrepancies reported in the literature for this nucleus.

The ^{17}O(p,α)^{14}N reaction plays a key role in various astrophysical scenarios, from asymptotic giant branch stars to classical novae. It affects the synthesis of rare isotopes such as ^{17}O and ^{18}F, which can provide constraints on astrophysical models. A new direct determination of the E_{R}=64.5 keV resonance strength performed at the Laboratory for Underground Nuclear Astrophysics (LUNA) accelerator has led to the most accurate value to date ωγ=10.0±1.4_{stat}±0.7_{syst} neV, thanks to a significant background reduction underground and generally improved experimental conditions. The (bare) proton partial width of the corresponding state at E_{x}=5672 keV in ^{18}F is Γ_{p}=35±5_{stat}±3_{syst} neV. This width is about a factor of 2 higher than previously estimated, thus leading to a factor of 2 increase in the ^{17}O(p, α)^{14}N reaction rate at astrophysical temperatures relevant to shell hydrogen burning in red giant and asymptotic giant branch stars. The new rate implies lower ^{17}O/^{16}O ratios, with important implications on the interpretation of astrophysical observables from these stars.

K. Hadyńska-Kl¸ek et al. ; 7 pags., 3 figs., 2 tabs., Shape parameters of a weakly deformed ground-state band and highly deformed slightly triaxial sideband in Ca42 were determined from E2 matrix elements measured in the first low-energy Coulomb excitation experiment performed with AGATA. The picture of two coexisting structures is well reproduced by new state-of-the-art large-scale shell model and beyond-mean-field calculations. Experimental evidence for superdeformation of the band built on 02+ has been obtained and the role of triaxiality in the A∼40 mass region is discussed. Furthermore, the potential of Coulomb excitation as a tool to study superdeformation has been demonstrated for the first time. © 2016 American Physical Society, Special gratitude goes to the INFN LNL and HIL Warsaw technical staff for their support and help, in particular, the accelerator crews for providing intense and good-quality 42Ca and 32S beams. K. H.-K. acknowledges support from the Research Council of Norway under the project Grant No. 213442. T. R. R. acknowledges computing time at GSI-Darmstadt and support from Spanish MINECO under Programa Ramon y Cajal 11420 and FIS-2014-53434-P, H. N. acknowledges support from Helmholtz Association through the Nuclear Astrophysics Virtual Institute NAVI (No. VH-VI-417). We also acknowledge the support by Generalitat Valenciana, Spain, under the grant PROMETEOII/2014/019 and by the FEDER funds of the European Commission (A. Gadea), Spanish Ministerio de Economía y Competitividad under Contract No. FPA2014-57196-C5 (A. J., A. Gadea), German Bundesministerium für Bildung und Forschung (BMBF) under Contract No. 05P12PKFNE TP4 (B. Birkenbach), the Polish National Science Centre under Projects No. DEC-2013/10/M/ST2/00427, No. DPN/N190/ AGATA/2009, No. 2011/03/B/ST2/01894, No. UMO- 2014/14/M/ST2/00738 (COPIN-INFN Collaboration), and No. 2015/17/B/ST2/01534.

We performed a γ -particle coincidence experiment for the 60Ni+116Sn system to investigate whether the population of the two-neutron pickup channel leading to 62Ni is mainly concentrated in the ground-state transition, as has been found in a previous work [D. Montanari et al., Phys. Rev. Lett. 113, 052501 (2014)]. The experiment has been performed by employing the PRISMA magnetic spectrometer coupled to theAdvanced Gamma Tracking Array (AGATA) demonstrator. The strength distribution of excited states corresponding to the inelastic, one- and two-neutron transfer channels has been extracted.We found that in the two-neutron transfer channel the strength to excited states corresponds to a fraction (less than 24%) of the total, consistent with the previously obtained results that the 2n channel is dominated by the ground-state to ground-state transition.

The γ decay from the high-lying states of ^140Ce excited via inelastic scattering of ^17O at a bombarding energy of 340 MeV was measured using the high-resolution AGATA-demonstrator array in coincidence with scattered ions detected in two segmented Δ E-E silicon detectors. Angular distributions of scattered ions and emitted γ rays were measured, as well as their differential cross sections. The excitation of 1^− states below the neutron separation energy is similar to the one obtained in reactions with the α isoscalar probe. The comparison between the experimental differential cross sections and the corresponding predictions using the distorted-wave Born approximation allowed us to extract the isoscalar component of identified 1^− pygmy states. For this analysis the form factor obtained by folding microscopically calculated transition densities and optical potentials was used.

When deriving resonance strengths using the thick-target yield approximation, for very narrow resonances it may be necessary to take beam energy straggling into account. This applies to gas targets of a few keV width, especially if there is some additional structure in target stoichiometry or detection efficiency. The correction for this effect is shown and tested on recent studies of narrow resonances in the and reactions.

The study of the collective properties of nuclear excitations far from stability provides information about the shell structure at extreme conditions. Spectroscopic ob- servables such as the energy or the transition probabilities of the lowest states, in nuclei with large neutron excess, allow to probe the density and isospin dependence of the ef- fective interaction. Indeed, it was recently shown that tensor and three-body forces play an important role in breaking and creating magic numbers. Emblematic is the case of the evolution of the Ni isotopic chain where several features showed up moving from the most neutron rich stable isotope ( 64 Ni) towards the 78 Ni nucleus where the large neutron excess coincides with a double shell closure. In this framework, we have recently per- formed an experiment with the goal to extract the B(E2; 0 + ! 2 + ) value for the 74 Ni nucleus in an intermediate-energy Coulomb excitation experiment: preliminary results are discussed.

Reduced quadrupole transition probabilities for low-lying transitions in neutron-rich Se-84,Se-86 are investigated with a recoil distance Doppler shift (RDDS) experiment. The experiment was perform ...

The ^{22}Ne(p,γ)^{23}Na reaction takes part in the neon-sodium cycle of hydrogen burning. This cycle affects the synthesis of the elements between ^{20}Ne and ^{27}Al in asymptotic giant branch stars and novae. The ^{22}Ne(p,γ)^{23}Na reaction rate is very uncertain because of a large number of unobserved resonances lying in the Gamow window. At proton energies below 400 keV, only upper limits exist in the literature for the resonance strengths. Previous reaction rate evaluations differ by large factors. In the present work, the first direct observations of the ^{22}Ne(p,γ)^{23}Na resonances at 156.2, 189.5, and 259.7 keV are reported. Their resonance strengths are derived with 2%-7% uncertainty. In addition, upper limits for three other resonances are greatly reduced. Data are taken using a windowless ^{22}Ne gas target and high-purity germanium detectors at the Laboratory for Underground Nuclear Astrophysics in the Gran Sasso laboratory of the National Institute for Nuclear Physics, Italy, taking advantage of the ultralow background observed deep underground. The new reaction rate is a factor of 20 higher than the recent evaluation at a temperature of 0.1 GK, relevant to nucleosynthesis in asymptotic giant branch stars.

The isospin mixing was deduced in the compound nucleus Zr-80 at an excitation energy of E* = 54 MeV from the gamma decay of the giant dipole resonance. The reaction Ca-40 + Ca-40 at E-beam = 136 MeV was used to form the compound nucleus in the isospin I = 0 channel, while the reaction Cl-37 + Ca-44 at E-beam = 95 MeV was used as the reference reaction. The. rays were detected with the AGATA demonstrator array coupled with LaBr3:Ce detectors. The temperature dependence of the isospin mixing was obtained and the zero-temperature value deduced. The isospin-symmetry-breaking correction delta(C) used for the Fermi superallowed transitions was extracted and found to be consistent with beta-decay data.

Background: Identification of proton-neutron mixed-symmetric one-quadrupole phonon excitations (the 2(ms)(+) states) of atomic nuclei provides information on the isovector part of the residual nucleon-nucleon interaction. It was predicted that the 2(ms)(+) state of particular nuclei close to the U(5) limit of the interacting boson model, in particular Ba-140, should be considerably populated by alpha-transfer reactions [C. E. Alonso et al., Phys. Rev. C 78, 017301 (2008)]. Purpose: We aim at the identification of the 2(ms)(+) mixed-symmetry state (MSS) of radioactive Ba-140 and investigate its population by the alpha-transfer reaction as a suitable tool to selectively populate MSSs and as a potential new signature for its mixed-symmetric character. Method: A gamma-ray spectroscopy experiment was performed in inverse kinematics in order to populate the 2(ms)(+) state of Ba-140 by alpha-transfer from a C-nat target on Xe-136 beam ions. The population of the candidate for the 2(ms)(+) state of Ba-140 was measured relative to the population of the 2(1)(+) state. Results: The candidate for the 2(ms)(+) state of Ba-140 was populated by a transfer three times weaker than predicted. Another 2(+) state that can be ruled out as the MSS was in turn as strongly populated by the a transfer as predicted for the MSS. Conclusions: The relative population of 2(+) states by alpha-transfer cannot serve as a new signature for MSSs, since other 2(+) states are also strongly populated. Nevertheless, the substantial population of the MSS candidate of Ba-140 by alpha transfer qualifies this type of reaction as suitable tool to excite MSSs and study their electromagnetic decay properties.

Background: Nuclear structure information for the neutron-rich actinide nuclei is important since it is the benchmark for theoretical models that provide predictions for the heaviest nuclei. Purpose: gamma-ray spectroscopy of neutron-rich heavy nuclei in the actinide region. Method: Multinucleon-transfer reactions in Zn-70 + U-238 and Xe-136 + U-238 have been measured in two experiments performed at the INFN Legnaro, Italy. In the Zn-70 experiment the high-resolution HPGe Clover Array (CLARA) coupled to the magnetic spectrometer PRISMA was employed. In the Xe-136 experiment the high-resolution Advanced Gamma Tracking Array (AGATA) was used in combination with PRISMA and the Detector Array for Multinucleon Transfer Ejectiles (DANTE). Results: The ground-state band (g.s. band) of U-240 was measured up to the 20(+) level and a tentative assignment was made up to the (24(+)) level. Results from gamma gamma coincidence and from particle coincidence analyses are shown. Moments of inertia (MoI) show a clear upbend. Evidence for an extended first negative-parity band of U-240 is found. Conclusions: A detailed comparison with latest calculations shows best agreement with cranked relativistic Hartree-Bogoliubov (CRHB) calculations for the g.s. band properties. The negative-parity band shows the characteristics of a K-pi = 0 band based on an octupole vibration.

Background: Multinucleon transfer reactions (MNT) are a competitive tool to populate exotic neutron-rich nuclei in a wide region of nuclei, where other production methods have severe limitations or cannot be used at all. Purpose: Experimental information on the yields of MNT reactions in comparison with theoretical calculations are necessary to make predictions for the production of neutron-rich heavy nuclei. It is crucial to determine the fraction of MNT reaction products which are surviving neutron emission or fission at the high excitation energy after the nucleon exchange. Method: Multinucleon transfer reactions in Xe-136 + U-238 have been measured in a high-resolution gamma-ray/particle coincidence experiment. The large solid-angle magnetic spectrometer PRISMA coupled to the high-resolution Advanced Gamma Tracking Array (AGATA) has been employed. Beamlike reaction products after multinucleon transfer in the Xe region were identified and selected with the PRISMA spectrometer. Coincident particles were tagged by multichannel plate detectors placed at the grazing angle of the targetlike recoils inside the scattering chamber. Results: Mass yields have been extracted and compared with calculations based on the GRAZING model for MNT reactions. Kinematic coincidences between the binary reaction products, i.e., beamlike and targetlike nuclei, were exploited to obtain population yields for nuclei in the actinide region and compared to x-ray yields measured by AGATA. Conclusions: No sizable yield of actinide nuclei beyond Z = 93 is found to perform nuclear structure investigations. In-beam gamma-ray spectroscopy is feasible for few-neutron transfer channels in U and the -2p channel populating Th isotopes.

High-spin states in the neutron-rich nuclei 172,173Yb have been populated in a 170Er(7Li,(p,d,t)xn) incomplete-fusion reaction and the emitted γ-radiation was detected with the GASP array. The signature partners of the 7/2+[633] rotational band of the odd-N 173Yb isotope have been newly established and were observed up to spin values of (45/2+) and (43/2+), respectively. The ground-state band of the even-even nucleus 172Yb has been observed up to a spin value of (22+). No band crossings were found in these bands. To explain this observation, it is proposed that the static pair field is absent, considering that the neutron odd-even mass differences reach for these nuclei very small values and that the band crossing is absent in cranked shell modell calculations without pairing. The results indicate, however, that strong dynamic correlations are still present.

The reactions 16O(7Li, 2n) and 16O(7Li, np) populating 21Na and 21Ne have been studied at E L=27 MeV using the GASP γ-detector array. The level schemes for 21Na and 21Ne have been extended to higher spin. The population of the bands with K=3/2 and 1/2, forming parity doublets, are compared. Preferential E1 decay between bands of opposite parity is observed in agreement with the octupole scenario. The structure of these bands can be interpreted as consisting of an instrinsic asymmetric (4He + 16O) structure with octupole deformation.

The reactions 16O(7Li, 2n) and 16O(7Li, np) populating 21Na and 21Ne have been studied at EL = 27 MeV using the GASP γ-detector array. The level scheme for 21Na and 21Ne has been extended to higher excitation energy. Spins and parities of the observed levels are assigned tentatively supporting the identification of opposite parity structures connected by strong dipole transitions. The structure of these bands is interpreted as based on a reflection asymmetric cluster structure.

2(+) and 1(-) states in Zr-90 were populated via the (O-17, O-17 'gamma) reaction at 340 MeV. The gamma decay was measured with high resolution using the AGATA (advanced gamma tracking array demonstrator array). Differential cross sections were obtained at few different angles for the scattered particle. The results of the elastic scattering and inelastic excitation of 2(+), 3(,)(-) and 1(-) states are compared with distorted-wave Born approximation (DWBA) calculations, using both the standard collective form factor and a form factor obtained by folding microscopically calculated transition densities. This allowed to extract the isoscalar component of the 1(-) state at 6.424 MeV. The comparison of the present (17O, 17O 'gamma) data with existing (gamma,gamma') and (p, p') data in the corresponding region of the gamma continuum (6-11 MeV), characterized by a large E1 component, shows completely different behaviors of the cross section as a function of the nuclear excitation energy. The comparison of the data with DWBA calculations suggests a decrease of the isoscalar strength in the cross section with increasing excitation energy.

1st NUBA International Conference on Nuclear Physics and Astrophysics -- SEP 14-21, 2014 -- Akdeniz Univ, Antalya, TURKEY, WOS: 000354773900036, High-spin states in Cl-36 were populated through the Mg-24(N-14,2p)Cl-36 reaction at E(N-14)=31 MeV. Lifetimes have been determined for fifteen states by applying the Doppler shift attenuation method. The results indicated the onset of collectivity in the high spin negative parity states. Large basis shell model calculations have been performed to understand the underlying structure of these states.

We have investigated the ability of AGATA triple clusters to measure the linear polarization of gamma rays, exploiting the azimuthal-angle dependence of the Compton scattering differential cross section. To this aim, partially polarized gamma rays have been produced by Coulomb excitation of the first excited state of 104Pd and 108Pd, which decay to the ground state by emission of gamma rays of 555.8 keV and 433.9 keV, respectively. Pulse-shape analysis and gamma-ray tracking techniques have been used to determine the position and time sequence of the interaction points inside the germanium crystals. Anisotropies in the detection efficiency have been taken into account using 661.6 keV gammas from a 137Cs radioactive source. We obtain an average analyzing power of 0.451(34) at 433.9 keV and 0.484(24) at 555.8 keV.

Spin distribution measurements were performed for the reaction 64 Ni + 100 Mo at three beam energies ranging from 230 to 260 MeV. Compound nucleus (CN) spin distributions were obtained channel selective for each evaporation residue populated by the de-excitation cascade. A comparison of the spin distribution at different beam energies indicates that its slope becomes steeper and steeper with increasing beam energy. This change in slope of the spin distribution is mainly due to the onset of fission competition with particle evaporation at higher beam energies.

Lifetimes have been determined using the Doppler Shift Attenu- ation Method in the N Z nuclei 46 V and 48 V nuclei, populated with the reaction 28 Si on 24 Mg at 115 MeV and 24 Mg on 28 Si at 100 MeV using Au and Pb backed targets. The coexistence of spherical and deformed states in the middle of the 1f7=2 shell is discussed. The B(E2) and B(M1) reduced rates agree very well with large scale shell model predictions.

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.

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

Recent observations of $^{6}\mathrm{Li}$ in metal poor stars suggest a large production of this isotope during big bang nucleosynthesis (BBN). In standard BBN calculations, the $^{2}\mathrm{H}(\ensuremath{\alpha},\ensuremath{\gamma})^{6}\mathrm{Li}$ reaction dominates $^{6}\mathrm{Li}$ production. This reaction has never been measured inside the BBN energy region because its cross section drops exponentially at low energy and because the electric dipole transition is strongly suppressed for the isoscalar particles $^{2}\mathrm{H}$ and $\ensuremath{\alpha}$ at energies below the Coulomb barrier. Indirect measurements using the Coulomb dissociation of $^{6}\mathrm{Li}$ only give upper limits owing to the dominance of nuclear breakup processes. Here, we report on the results of the first measurement of the $^{2}\mathrm{H}(\ensuremath{\alpha},\ensuremath{\gamma})^{6}\mathrm{Li}$ cross section at big bang energies. The experiment was performed deep underground at the LUNA 400 kV accelerator in Gran Sasso, Italy. The primordial $^{6}\mathrm{Li}/^{7}\mathrm{Li}$ isotopic abundance ratio has been determined to be $(1.5\ifmmode\pm\else\textpm\fi{}0.3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$, from our experimental data and standard BBN theory. The much higher $^{6}\mathrm{Li}/^{7}\mathrm{Li}$ values reported for halo stars will likely require a nonstandard physics explanation, as discussed in the literature.

The properties of pygmy dipole states in Pb-208 were investigated using the Pb-208(O-17, O-17'gamma) reaction at 340 MeV and measuring the gamma decay with high resolution with the AGATA demonstrator array. Cross sections and angular distributions of the emitted gamma rays and of the scattered particles were measured. The results are compared with (gamma, gamma') and (p, p') data. The data analysis with the distorted wave Born approximation approach gives a good description of the elastic scattering and of the inelastic excitation of the 2(+) and 3(-) states. For the dipole transitions a form factor obtained by folding a microscopically calculated transition density was used for the first time. This has allowed us to extract the isoscalar component of the 1(-) excited states from 4 to 8 MeV.

The near proton drip-line nucleus 126Pr was studied via in-beam γ-ray spectroscopy using the 40Ca+82Mo reaction at 190 MeV. We observed for the first time excited states above the known isomer in this nucleus, up to spin 31h. The observed band is assigned to a πh 11/2 ⋇ νh 11/2 configuration. The experimental information suggest a spin 8+ for the lowest observed state. With such a spin assignment the excitation energy of the excited states in 126Pr and 128Pr get smaller than in the heavier Pr isotopes, suggesting a sudden change in deformation close to the proton drip line.

In stars, four hydrogen nuclei are converted into a helium nucleus in two competing nuclear fusion processes, namely the proton-proton chain (p-p chain) and the carbon-nitrogen-oxygen (CNO) cycle. For temperatures above 20 million kelvin, the CNO cycle dominates energy production, and its rate is determined by the slowest process, the 14N(p,γ)15O radiative capture reaction. This reaction proceeds through direct and resonant capture into the ground state and several excited states in 15O. High energy data for capture into each of these states can be extrapolated to stellar energies using an R-matrix fit. The results from several recent extrapolation studies are discussed. A new experiment at the LUNA (Laboratory for Underground Nuclear Astrophysics) 400kV accelerator in Italy's Gran Sasso laboratory measures the total cross section of the 14N(p,γ)15O reaction with a windowless gas target and a 4π BGO summing detector, down to center of mass energies as low as 70keV. After reviewing the characteristics of the LUNA facility, the main features of this experiment are discussed, as well as astrophysical scenarios where cross section data in the energy range covered have a direct impact, without any extrapolation.

The nucleus 35S has been studied by in-beam ?-ray spectroscopy using the 24Mg(14N,3p) fusion-evaporation reaction at Elab=40 MeV. A level scheme extended up to J?=17/2+ at 8023 keV and J?=13/2- at 6352 keV has been established. Lifetimes of six excited states have been determined by applying the Doppler shift attenuation method. The experimental data have been compared with the results of large-scale shell model calculations performed using different effective interactions and model spaces allowing particle-hole excitations across the N=Z=20 shell gap. © 2014 American Physical Society.

The detection of the 1809 keV emission line associated with the decay of 26 Al in the interstellar medium provides a direct evidence of recent nucleosynthesis events in our galaxy. 26 Al is thought to be mainly produced in massive stars, but in order to have a quantita- tive understanding of the 26 Al distribution, the cross section of all the nuclear reactions involved in its production should be accurately known. A recent sensitivity study demonstrated that the 25 Mg( ,n) 28 Si is the reaction with the strongest impact on the synthesis of 26 Al during explosive Neon and Carbon burning (4). In order to improve the experimental knowledge of the 25 Mg( ,n) 28 Si cross section, a new direct measurement has been performed at Legnaro National Laboratories. The experimental setup, the data analysis and preliminary results are discussed.