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Background: A recent sensitivity study has shown that the K35(p,γ)Ca36 reaction is one of the ten (p,γ) reaction rates that could significantly impact the shape of the calculated x-ray burst light curve. Its reaction rate used up to now in type I x-ray burst calculations was estimated using an old measurement for the mass of Ca36 and theoretical predictions for the partial decay widths of the first 2+ resonance with arbitrary uncertainties. Purpose: In this work, we propose to reinvestigate the K35(p,γ)Ca36 reaction rate, as well as related uncertainties, by determining the energies and decay branching ratios of Ca36 levels, within the Gamow window of x-ray bursts, in the 0.5 to 2 GK temperature range. Method: These properties were studied by means of the one-neutron pickup transfer reaction Ca37(p,d)Ca36 in inverse kinematics using a radioactive beam of Ca37 at 48 MeV nucleon−1. The experiment was performed at the GANIL facility using the liquid hydrogen target CRYPTA, the MUST2 charged particle detector array for the detection of the light charged particles, and a zero degree detection system for the outgoing heavy recoil nuclei. Results: The atomic mass of Ca36 is confirmed and new resonances have been proposed together with their proton decay branching ratios. This spectroscopic information, used in combination with very recent theoretical predictions for the γ-decay width, were used to calculate the K35(p,γ)Ca36 reaction rate. The recommended rate of the present work was obtained within a uncertainty factor of 2 at 1σ. This is consistent with the previous estimate in the x-ray burst temperature range. A large increase of the reaction rate was found at higher temperatures due to two newly discovered resonances. Conclusions: The K35(p,γ)Ca36 thermonuclear reaction rate is now well constrained by the present work in a broad range of temperatures covering those relevant to type I x-ray bursts. Our results show that the K35(p,γ)Ca36 reaction does not affect the shape of the x-ray burst light curve, and that it can be removed from the list of the few influential proton radiative captures reactions having a strong impact on the light curve.

Spatially-correlated overabundances of $^{15}$N and $^{18}$O observed in some low-density graphite meteoritic grains have been connected to nucleosynthesis taking place in the helium-burning shell during core-collapse supernovae. Two of the reactions which have been identified as important to the final abundances of $^{15}$N and $^{18}$O are $^{18}$F($n,\alpha$)$^{15}$N and $^{18}$F($n,p$)$^{18}$O. The relative strengths of the $^{18}$F($n,\alpha$)$^{15}$N and $^{18}$F($n,p$)$^{18}$O reactions depend on the relative $\alpha_0$ and $p_0$ decays from states above the neutron threshold in $^{19}$F in addition to other properties. Experimental data on the charged-particle decays from these highly excited states are lacking or inconsistent. Two experiments were performed using proton inelastic scattering from LiF targets and magnetic spectrographs. The first experiment used the high-resolution Q3D spectrograph at Munich to constrain properties of levels in $^{19}$F. A second experiment using the Orsay Split-Pole spectrograph and an array of silicon detectors was performed in order to measure the charged-particle decays of neutron-unbound levels in $^{19}$F. A number of levels in $^{19}$F have been identified along with their corresponding charged-particle decays. The first state above the neutron threshold which has an observed proton-decay branch to the ground state of $^{18}$O lies 68 keV above the neutron threshold while the $\alpha$-particle decays from the neutron-unbound levels are generally observed to be much stronger than the proton decays. Neutron-unbound levels in $^{19}$F are observed to decay predominantly by $\alpha$-particle emission, supporting the role of $^{18}$F($n,\alpha$)$^{15}$N in the production of $^{15}$N in the helium-burning shell of supernovae. Improved resonant-scattering reaction data are required in order to be able to determine the reaction rates accurately.

The tetraneutron has attracted the attention of nuclear physicists during the past decades, but there is still no unambiguous confirmation of its existence or non-existence. A new experiment based on $$^{8}$$ He(p, 2p) $$^{7}$$ H{t+ $$^{4}n$$ } reaction, with direct detection of the four neutrons, has been carried out at RIBF, which can hopefully help to draw a definite conclusion on the tetraneutron system.

The structure of a neutron-rich ^{25}F nucleus is investigated by a quasifree (p,2p) knockout reaction at 270A MeV in inverse kinematics. The sum of spectroscopic factors of π0d_{5/2} orbital is found to be 1.0±0.3. However, the spectroscopic factor with residual ^{24}O nucleus being in the ground state is found to be only 0.36±0.13, while those in the excited state is 0.65±0.25. The result shows that the ^{24}O core of ^{25}F nucleus significantly differs from a free ^{24}O nucleus, and the core consists of ∼35% ^{24}O_{g.s.}. and ∼65% excited ^{24}O. The result may infer that the addition of the 0d_{5/2} proton considerably changes neutron structure in ^{25}F from that in ^{24}O, which could be a possible mechanism responsible for the oxygen dripline anomaly.

The MUGAST-AGATA-VAMOS set-up at GANIL combines the MUGAST highly-segmented silicon array with the state-of-the-art AGATA array and the large acceptance VAMOS spectrometer. The mechanical and electronics integration copes with the constraints of maximum efficiency for each device, in particular {\gamma}-ray transparency for the silicon array. This complete set-up offers a unique opportunity to perform exclusive measurements of direct reactions with the radioactive beams from the SPIRAL1 facility. The performance of the set-up is described through its commissioning and two examples of transfer reactions measured during the campaign. High accuracy spectroscopy of the nuclei of interest, including cross-sections and angular distributions, is achieved through the triple-coincidence measurement. In addition, the correction from Doppler effect of the {\gamma}-ray energies is improved by the detection of the light particles and the use of two-body kinematics and a full rejection of the background contributions is obtained through the identification of heavy residues. Moreover, the system can handle high intensity beams (up to 108 pps). The particle identification based on the measurement of the time-of-flight between MUGAST and VAMOS and the reconstruction of the trajectories is investigated., Comment: 13 pages, 18 figures

International audience; We measured the α-clustering strength at the surface of tin isotopes ^112,116,120,124Sn by using quasi-free \((p,p\alpha )\) reaction at RCNP. Formation of α clusters at the surface of tin isotopes was clearly evidenced from our results. Surface α-clustering in heavy nuclei provides a natural explanation for the origin of α particles in α decay, and may also impact the neutron-skin thickness which plays a critical role in constraining the nuclear symmetry energy.

International audience; α-clustering strength at the surface of tin isotopes ^112,116,120,124Sn was measured by using quasi-free (p, pα) reaction at RCNP. By measuring the scattered protons and α particles in coincidence, formation of α clusters at the surface of tin isotopes was clearly evidenced. Surface α-clustering in heavy nuclei provides a natural explanation for the origin of α particles in α decay, and may also impact the neutron-skin thickness which plays an important role in constraining the nuclear symmetry energy.

International audience; Differential cross sections of p–6He elastic scattering were measured in inverse kinematics at an incident energy of 200 A MeV, covering the high momentum transfer region of 1.7–2.7 fm−1. The sensitivity of the elastic scattering at low and high momentum transfers to the density distribution was investigated quantitatively using relativistic impulse approximation calculations. In the high momentum transfer region, where the present data were taken, the differential cross section has an order of magnitude higher sensitivity to the inner part of the 6He density relative to the peripheral part (15:1). This feature makes the obtained data valuable for the deduction of the inner part of the 6He density. The data were compared to a set of calculations assuming different proton and neutron density profiles of 6He. The data are well reproduced by the calculation assuming almost the same profiles of proton and neutron densities around the center of 6He, and a proton profile reproducing the known point-proton radius of 1.94 fm. This finding is consistent with the assumption that the 6He nucleus consists of a rigid α-like core with a two-neutron halo.

International audience; The dependence of the single-particle strength on the difference between proton and neutron separation energies is studied for oxygen isotopes in a wide range of isospins. The cross sections of the quasi-free (p, 2p) reaction on 14,16,18,22,24O were measured at intermediate energies. The measured cross sections are compared to predictions based on the distorted wave impulse approximation and shell-model psd valence-space spectroscopic factors. The reduction factors, which are the ratio of the experimental cross sections to the theoretical predictions, show no apparent dependence on the proton–neutron separation energy difference. The result is compatible with the result of the (e, e p) reaction on stable targets and with the predictions of recent ab initio calculations.

The unbound O12 nucleus was studied via the two-neutron transfer (p,t) reaction in inverse kinematics using a radioactive O14 beam at 51 MeV/u. Excitation energy spectra and differential cross sections were deduced by the missing mass method using MUST2 telescopes. We achieved much higher statistics compared to the previous experiments of O12, which allowed accurate determination of resonance energy and unambiguous spin and parity assignment. The O12 resonance previously reported using the same reaction was confirmed at an excitation energy of 1.62±0.03(stat.)±0.10(syst.). MeV and assigned spin and parity of 0+ from a distorted-wave Born approximation analysis of the differential cross sections. Mirror symmetry of O12 with respect to its neutron-rich partner Be12 is discussed from the energy difference of the second 0+ states. In addition, from systematics of known 0+ states, a distinct correlation is revealed between the mirror energy difference and the binding energy after carrying out a scaling with the mass and the charge. We show that the mirror energy difference of the observed 0+ state of O12 is highly deviated from the systematic trend of deeply bound nuclei and in line with the scaling relation found for weakly bound nuclei with a substantial 2s1/2 component. The importance of the scaling of mirror asymmetry is discussed in the context of ab initio calculations near the drip lines and universality of few-body quantum systems.

Experiments based on the isomer-spectroscopy method were performed using the secondary beam line at RCNP, Osaka University. Recently, a new γ-ray spectroscopy method was established using fusion reaction induced by low-energy RI beam. This method enables us to study high-spin states of nuclei in wider mass region where it is difficult to populate them by using the combination of stable beams and stable targets. This method works well although low production of nuclei, because (1) the combination of beams and targets can be selected with large-reaction cross section and (2) high-S/N measurement can be performed by the event-by-event detection to select the events correlated with RI beam, which reduces background γ rays, competing with γ rays emitted from fusion products. As the first step, high-spin states of 142 Pr were studied using fusion reaction induced by low-energy 17 N RI beam. Large cross section was obtained by the 130 Te (17 N ,5 n ) reaction with 4.9 MeV/u 17 N beam. Event selection, which was carried out by the event-by-event detection with low-beam intensity of 2×104 pps, enables high-S/N measurement.

We present the first missing mass spectrum of the unbound nucleus He10, measured at RIKEN using the Li11(d,He3) reaction at 50A MeV. He10 is believed to be a three-body He8+n+n resonance beyond the limit of nuclear binding. Our observation of a new decay branch, 6He+4n, and of a puzzling reduction of the Li11(d,He3)He10 cross section challenges this view. Moreover, our experiment shows a new trend in the evolution of the proton spectroscopic strength in Li isotopes deduced from the comparison of the (d,He3) cross sections on Li7,8,9,11 with theoretical predictions. We discuss new questions about physics beyond the limits of nuclear existence raised by these findings.

The cosmological 7Li problem arises from the signi cant discrepancy of about a factor 3 between the predicted primordial 7Li abundance and the observed one. The main process for the production of 7Li during Big-Bang nucleosynthesis is the decay of 7Be. Many key nuclear reactions involved in the production and destruction of 7Be were investigated in attempt to explain the 7Li de cit but none of them led to successful conclusions. However, some authors suggested recently the possibility that the destruction of 7Be by 3He and 4He may reconcile the predictions and observations if missing resonant states in the compound nuclei 10C and 11C exist. Hence, a search of these missing resonant states in 10C and 11C was investigated at the Orsay Tandem-Alto facility through 10B(3He,t)10C and 11B(3He,t)11C charge-exchange reactions respectively. After a short overview of the cosmological 7Li problem from a nuclear physics point of view, a description of the Orsay experiment will be given as well as the obtained results and their impact on the 7Li problem.

High-spin states in the odd-odd nucleus La136, which is located close to the β-stability line, have been investigated in the radioactive-beam-induced fusion-evaporation reaction Sn124(N17,5n). The use of the radioactive beam enabled a highly sensitive and successful search for a new isomer [14+,T1/2=187(27) ns] in La136. In the A=130–140 mass region, no such long-lived isomer has been observed at high spin in odd-odd nuclei. The La136 level scheme was revised, incorporating the 14+ isomer and six new levels. The results were compared with pair-truncated shell model (PTSM) calculations which successfully explain the level structure of the πh11/2⊗νh−111/2 bands in La132 and La134. The isomerism of the 14+ state was investigated also by a collective model, the cranked Nilsson-Strutinsky (CNS) model, which explains various high-spin structures in the medium-heavy mass region. It is suggested that a new type of collective structure is induced in the PTSM model by the increase of the number of πg7/2 pairs, and/or in the CNS model by the configuration change associated with the shape change in La136.

International audience; We present the first missing mass spectrum of the unbound system 10He obtained from one nucleon transfer $^{11}$Li(d,$^{3}$He) reaction at 50 A MeV. We found rather large yields for the $^{6}$He + 4n decay channel especially for higher excitation energy, which suggest the importance of the $^{6}$He + 4n structure in $^{10}$He.

Expérience GANIL/MUST2; International audience; We have measured the 72Zn(d, 3He) 71Cu proton pickup reaction in inverse kinematics at 38 MeV/u. A dedicated setup was developed to overcome the experimental challenges posed by the low cross section of the reaction and the low energy of the outgoing 3He particles. The excitation-energy spectrum was reconstructed and spectroscopic factors were obtained after analysis of the angular distributions in the finite-range Distorted-Wave Born Approximation (DWBA). The results show that unlike for the πf5/2 orbital, the πf7/2 single-particle strength is not appreciably affected by the addition of neutrons beyond N = 40.

The observed primordial ${}^{7}$Li abundance in metal-poor halo stars is found to be lower than its Big-Bang nucleosynthesis (BBN) calculated value by a factor of approximately three. Some recent works suggested the possibility that this discrepancy originates from missing resonant reactions which would destroy ${}^{7}$Be, parent of ${}^{7}$Li. The most promising candidate resonances which were found include a possibly missed 1${}^{\ensuremath{-}}$ or 2${}^{\ensuremath{-}}$ narrow state around 15 MeV in the compound nucleus ${}^{10}$C formed by ${}^{7}$Be+${}^{3}$He and a state close to 7.8 MeV in the compound nucleus ${}^{11}$C formed by ${}^{7}$Be+${}^{4}$He. In this work, we studied the high excitation energy region of ${}^{10}$C and the low excitation energy region in ${}^{11}$C via the reactions ${}^{10}$B(${}^{3}$He,$t$)${}^{10}$C and ${}^{11}$B(${}^{3}$He,$t$)${}^{11}$C, respectively, at the incident energy of 35 MeV. Our results for ${}^{10}$C do not support ${}^{7}$Be+${}^{3}$He as a possible solution for the ${}^{7}$Li problem. Concerning ${}^{11}$C results, the data show no new resonances in the excitation energy region of interest and this excludes the ${}^{7}$Be+${}^{4}$He reaction channel as an explanation for the ${}^{7}$Li deficit.

A study of the reaction {sup 48}Ca({sup 20}Ne,{sup 19}Ne {ital n}) at 48{ital A} MeV has been performed at the GANIL facility. The inclusive excitation spectrum above 12 MeV excitation is dominated by a broad structureless bump. Calculations performed in the framework of the Bonaccorso-Brink model predict that the absorption process (transfer+inelastic breakup) dominates over the elastic breakup process. Comparison of the neutron multiplicity calculated in a statistical model with the measured one confirms a significant contribution of the direct processes (elastic and inelastic breakup). The neutron yield to the ground state of the {sup 48}Ca is maximal in the forward direction. Comparisons with calculated neutron angular distributions show the effect of the final state interaction.

Inelastic scattering of 50 MeV/nucleon [sup 40]Ca on [sup 40]Ca was measured in coincidence with protons in order to investigate the excitation and decay of highly excited states in [sup 40]Ca. The proton decay pattern corresponding to an excitation region around 34 MeV shows the characteristic behavior expected of the direct decay of a two-phonon state. Thus, by using this novel method, the presence of a double-phonon state built with isoscalar giant resonances in [sup 40]Ca is demonstrated.

Giant resonances in 90 Zr and 208 Pb have been studied by inelastic scattering of 40 Ar at 41 MeV/u. Strength distributions and exhausted sum-rule values of different multipolarities are presented. The peak-to-background ratios and differential cross sections from inelastic scattering of heavy ions are compared to those obtained with light projectiles. The influence of Coulomb interaction on the excitation of giant resonances and the possibility to study high multipole resonances by intermediate-energy heavy ions are discussed.

Differential cross section of the inelastic scattering of a 54 MeV/nucleon {sup 26}Ne beam on a lead target has been measured by detecting the deexcitation {gamma}-rays. Analysis of the first 2{sup +} state angular distribution of the inelastically scattered nuclei shows that the process cannot be considered as a pure Coulomb excitation, and nuclear contribution must be taken into account. The charge deformation deduced, {beta}{sub 2}{sup C}=0.392{+-}0.024, corresponds to a B(E2)=141{+-}18 e{sup 2} fm{sup 2} in agreement with a N=16 subshell closure.

To investigate the behavior of the N=14 neutron gap far from stability with a neutron-sensitive probe, proton elastic and 2{sub 1}{sup +} inelastic scattering angular distributions for the neutron-rich nucleus {sup 22}O were measured using the MUr a STrip detector array at the Grand Accelerateur National d'Ions Lourds facility. A deformation parameter {beta}{sub p,p{sup '}}=0.26{+-}0.04 is obtained for the 2{sub 1}{sup +} state, much lower than in {sup 20}O, showing a weak neutron contribution to this state. A microscopic analysis was performed using matter and transition densities generated by continuum Skyrme-Hartree-Fock-Bogoliubov and quasiparticle random phase approximation calculations, respectively. The ratio of neutron to proton contributions to the 2{sub 1}{sup +} state is found close to the N/Z ratio, demonstrating a strong N=14 shell closure in the vicinity of the neutron drip line.

International audience; A large area telescope for measurements with radioactive beams in inverse kinematics for transfer reactions or unbound final states is described. The performance and the first beam tests results are described.

The ^18F(p, alpha)^15O reaction is recognized as one of the most important reaction for nova gamma-ray astronomy as it governs the early =< 511 keV emission. However, its rate remains largely uncertain at nova temperatures due to unknown low-energy resonance strengths. In order to better constrain this reaction rate, we have studied the one-nucleon transfer reaction, D(^18F,p alpha)^15N, at the CRC-RIB facility at Louvain La Neuve., Contribution to The Seventh International Symposium on Nuclei in the Cosmos

The 18F(p,alpha) reaction was recognized as one of the most important for gamma ray astronomy in novae as it governs the early 511 keV emission. However, its rate remains largely uncertain at nova temperatures. A direct measurement of the cross section over the full range of nova energies is impossible because of its vanishing value at low energy and of the short 18F lifetime. Therefore, in order to better constrain this reaction rate, we have performed an indirect experiment taking advantage of the availability of a high purity and intense radioactive 18F beam at the Louvain La Neuve RIB facility. We present here the first results of the data analysis and discuss the consequences., Contribution to the Classical Novae Explosions conference, Sitges, Spain, 20-24 May 2002, 5 pages, 3 figures

A novel experimental approach has been employed for the measurement of $\ensuremath{\beta}$-delayed protons from ${}^{24}\mathrm{Si}$ produced via the fragmentation of a ${}^{28}\mathrm{Si}$ beam with an energy of 100 MeV/nucleon. The secondary beam of ${}^{24}\mathrm{Si}$ was separated by the projectile fragment separator RIPS at RIKEN and was implanted in a 2.6 $\ensuremath{\mu}\mathrm{m}$ aluminum foil placed parallel to a gas-$\ensuremath{\Delta}E$ and silicon-$E$ detector telescope for the measurement of delayed protons. The above arrangement has led to a very clean, $\ensuremath{\beta}$-ray background free delayed proton energy spectra and a few new proton peaks could be identified from the decay of ${}^{24}\mathrm{Si}.$

Inelastic scattering of heavy ions has been extensively used to study the nuclear excitations. In particular the decay of giant resonances has been investigated to infer information on their microscopic structure1. In addition to the target excitation several processes are known to contribute to the inclusive inelastic spectrum. The quasi-elastic knock-out process is a major contribution in the inelastic scattering of protons and α-particle projectiles. For heavier ions this contribution is expected to be smaller but still persists. Proton emission coming from the knock-out process was clearly observed and was detected in the direction of the recoiling target nucleus. Another process contributing to the inclusive inelastic spectrum is the pick-up break-up process2. In this process the projectile picks up a nucleon from the target, leaving it in a 1-hole configuration. The ejectile will then break-up again and feed the inelastic channel. This process gives rise to a plateau spreading over a large energy interval centered slightly above the bombarding energy per nucleon, with a width determined by the specific decay characteristics of the system.

The neutron drip line determination up to fluorine has been performed by projectile fragmentation of a 94.1AMeV 40Ar beam at the fragment separator RIPS at RIKEN. A new neutron-rich isotope 31F has been observed for the first time while clear evidence for the particle instability of 25N and 28O has been obtained. The sudden change of stability from oxygen to fluorine may demonstrate the onset of a deformation for the neutron-rich fluorine isotopes.

High-lying excitations were studied by means of the {sup 207}Pb{r_arrow}{sup 208}Pb, {sup 209}Bi{r_arrow}{sup 210}Bi, and {sup 59}Co{r_arrow}{sup 60}Ni stripping reactions and {sup 209}Bi{r_arrow}{sup 208}Pb and {sup 63}Cu{r_arrow}{sup 62}Ni pickup reactions induced by {sup 20}Ne and {sup 36}Ar projectiles at 48 and 42 MeV/nucleon, respectively. In the stripping spectra, structures a few MeV wide are observed at excitation energies of 10{endash}15 MeV, embedded in a large continuum. The corresponding {ital Q} values suggest that these structures are predominantly due to single-particle excitations rather than to the excitation of collective states such as giant resonances. This interpretation is in agreement with a microscopic calculation showing that in the one-nucleon transfer reactions only a small part of the cross section is due to the collective excitations. The overall shape of the neutron stripping spectra is well reproduced by the semiclassical reaction model of Bonaccorso and Brink, which treats on the same footing both the breakup of the projectile and the transfer to single-particle resonances. {copyright} {ital 1996 The American Physical Society.}

It has been shown that the neutron 2d5=2 orbital has to be included in shell-model calculations to explain the large quadrupole collectivity observed in the Fe and Cr of N = 40 region, probably a new island of inversion similar to the one known for light nuclei around N = 20. Indeed, in these calculations using a large valence neutron space, the position, i.e. the singleparticle energy, of the 2d5=2 orbital is a crucial ingredient. The experiment discussed in this paper aims to determine the $\nu$1g9=2–$\nu$2d5=2 gap using the neutron stripping reaction d(68Ni; p)68Ni which has been performed at GANIL in inverse kinematics. Preliminary results are presented.

We present an anlytical formula for the calculation of the anharmonicity of the two-phonon states which is based on a variational derivation of RPA-like equations for a many-fermion system. Analytical estimations of the anharmonicity have been made using the Lipkin model and a degenerated schematic model. The formula obtained, together with the extended RPA predictions, has been checked by comparison with the exact solutions of the models. A rough estimate of the anharmonicity of the two-phonon state built on the Giant Dipole Resonance and on the Giant Quadrupole Resonance has been deduced.

Spectromètre SPEG; The giant resonance region in the inelastic spectra from the reactions 20Ne + 90Zr and 20Ne + 208Pb at 40 MeV/nucleon has been studied with good energy and angular resolutions. The strength distributions of the different multipolarities contributing to the cross section were obtained without making any hypothesis on the excitation energies and shapes of the resonances. In the case of 208Pb the GDR strength was found to be strongly shifted towards lower excitation energies which can be explained by the exponentially decreasing Coulomb excitation probability. Furthermore, indications for a high multipolarity component in the resonance structure were found in both reactions.

Velocity and angular distributions of projectile-like fragments were measured between theta/sub lab/ = 0/sup 0/ and 4/sup 0/ (inside the grazing angle) for the /sup 40/Ar+ /sup 208/Pb system at 60 MeV/nucleon using a magnetic spectrometer. Velocity spectra are similar to those obtained at larger angles, while the angular distributions, very forward peaked for light nuclei, tend to become flat for the heaviest fragments. The influence of the Coulomb and nuclear deflection of the fragments is discussed.

International audience; 26Al was the first cosmic radioactivity ever detected in the galaxy. Its nucleosynthesis in novae outbursts is still uncertain mainly due to the lack of nuclear information concerning the 25Al(p,g )26Si reaction. We report here on a neutron-gamma coincidence measurement of the 24Mg(3He,ng )26Si reaction performed at the Orsay TANDEM facility aiming at the spectroscopic study of astrophysically important 26Si states. A new level in the Gamow peak is observed at EX = 5:888 MeV and the gamma-ray decay scheme of all levels below the proton threshold is confirmed.

The harmonic oscillator shell closure at N=40 in 68Ni is weak and loses its strength when removing (or adding) pair of protons. Calculations performed in this mass region predict a new island of inversion at N=40 similar to the one at N=20. Using a large valence space, the neutron orbital 2d5/2 is shown to be a crucial ingredient for the interpretation of the nuclear structure at N≈40. The neutron 1g9/2-2d5/2 energy difference has been determined in 69Ni using the d(68Ni,p) transfer reaction in inverse kinematics. The experiment performed at GANIL used a 68Ni beam at 25.14 MeV/u seperated by the LISE3 spectrometer was impinging a CD2 target of 2.6 mg/cm2 thickness. The experimental setup consisted of CATS/MUST2-S1/EXOGAM detectors coupled to an ionization chamber and a plastic scintillator. The angular momenta and spectroscopic factors of the ground state (Jπ = 9/2+) and a doublet of states ( Jπ = 5/2+) around 2.48 MeV corresponding to the population of the 1g9/2 and the 2d5/2 orbitals, were obtained from the comparison between the experimental cross-sections as a function of the proton detection angle and ADWA calculations. The spins of the observed states were assigned by comparaison to large scale Shell-Model calculations. The position of the 2d5/2 orbital in 69Ni has been established for the first time. Our measurements support the hypothesis of a low-lying 2d5/2 orbital (≈2.5 MeV) with respect to the 1g9/2 neutron orbital and thus its major role in the structure of the nuclei around N=40.; La fermeture de couche de l'oscillateur harmonique à N=40 dans le 68Ni est faible et perd sa rigidité après l'enlèvement (ou l'ajout) de paires de protons. Les calculs effectués dans cette région de masse prédisent un nouvel îlot d'inversion à N=40 semblable à celui à N=20 et montrant que le placement de l'orbital neutron 2d5/2 est un ingrédient essentiel pour l'interprétation de la structure nucléaire à N≈40. La différence d'énergie 1g9/2-2d5/2 a été déterminée dans le noyau 69Ni en utilisant la réaction de transfert d'un neutron d(68Ni,p) en cinématique inverse. L'expérience réalisée au GANIL utilisait un faisceau de 68Ni à 25,14 MeV/u. Les noyaux 68Ni séparés par le spectromètre LISE3 ont ensuite interagit avec une cible de CD2 d'épaisseur 2,6 mg/cm2. Le dispositif expérimental était composé principalement des détecteurs CATS/MUST2-S1/EXOGAM couplés à une chambre d'ionisation et un scintillateur plastique. Les moments angulaires et les facteurs spectroscopiques de l'état fondamental (Jπ = 9/2+) et d'un doublet d'états (Jπ = 5/2+) autour de 2,48 MeV, associés à la population des orbitales 1g9/2 et 2d5/2, ont été obtenus après la comparaison des sections efficaces différentielles et des calculs ADWA. Les spins des états observés ont été attribués après comparaison aux calculs de modèles en couches dans un grand espace de valence. La position de l'orbitale 2d5/2 dans 69Ni a été établie pour la première fois. Nos mesures confirment l'hypothèse de la faible différence d'énergie (≈2,5 MeV) entre l'orbitale neutron 2d5/2 et l'orbitale 1g9/2 et son importance pour décrire la structure des noyaux autour de N=40.

The harmonic oscillator shell closure at N=40 in 68Ni is weak and loses its strength when removing (or adding) pair of protons. Calculations performed in this mass region predict a new island of inversion at N=40 similar to the one at N=20. Using a large valence space, the neutron orbital 2d5/2 is shown to be a crucial ingredient for the interpretation of the nuclear structure at N≈40. The neutron 1g9/2-2d5/2 energy difference has been determined in 69Ni using the d(68Ni,p) transfer reaction in inverse kinematics. The experiment performed at GANIL used a 68Ni beam at 25.14 MeV/u seperated by the LISE3 spectrometer was impinging a CD2 target of 2.6 mg/cm2 thickness. The experimental setup consisted of CATS/MUST2-S1/EXOGAM detectors coupled to an ionization chamber and a plastic scintillator. The angular momenta and spectroscopic factors of the ground state (Jπ = 9/2+) and a doublet of states ( Jπ = 5/2+) around 2.48 MeV corresponding to the population of the 1g9/2 and the 2d5/2 orbitals, were obtained from the comparison between the experimental cross-sections as a function of the proton detection angle and ADWA calculations. The spins of the observed states were assigned by comparaison to large scale Shell-Model calculations. The position of the 2d5/2 orbital in 69Ni has been established for the first time. Our measurements support the hypothesis of a low-lying 2d5/2 orbital (≈2,5 MeV) with respect to the 1g9/2 neutron orbital and thus its major role in the structure of the nuclei around N=40.; La fermeture de couche de l'oscillateur harmonique à N=40 dans le 68Ni est faible et perd sa rigidité après l'enlèvement (ou l'ajout) de paires de protons. Les calculs effectués dans cette région de masse prédisent un nouvel îlot d'inversion à N=40 semblable à celui à N=20 et montrant que le placement de l'orbital neutron 2d5/2 est un ingrédient essentiel pour l'interprétation de la structure nucléaire à N≈40. La différence d'énergie 1g9/2-2d5/2 a été déterminée dans le noyau 69Ni en utilisant la réaction de transfert d'un neutron d(68Ni,p) en cinématique inverse. L'expérience réalisée au GANIL utilisait un faisceau de 68Ni à 25,14 MeV/u. Les noyaux 68Ni séparés par le spectromètre LISE3 ont ensuite interagit avec une cible de CD2 d'épaisseur 2,6 mg/cm2. Le dispositif expérimental était composé principalement des détecteurs CATS/MUST2-S1/EXOGAM couplés à une chambre d'ionisation et un scintillateur plastique. Les moments angulaires et les facteurs spectroscopiques de l'état fondamental (Jπ = 9/2+) et d'un doublet d'états ( Jπ = 5/2+) autour de 2,48 MeV, associés à la population des orbitales 1g9/2 et 2d5/2, ont été obtenus après la comparaison des sections efficaces différentielles et des calculs ADWA. Les spins des états observés ont été attribués après comparaison aux calculs de modèles en couches dans un grand espace de valence. La position de l'orbitale 2d5/2 dans 69Ni a été établie pour la première fois. Nos mesures confirment l'hypothèse de la faible différence d'énergie (≈2,5 MeV) entre l'orbitale neutron 2d5/2 et l'orbitale 1g9/2 et son importance pour décrire la structure des noyaux autour de N=40.

The harmonic oscillator shell closure at N=40 in 68Ni is weak and loses its strength when removing (or adding) pair of protons. Calculations performed in this mass region predict a new island of inversion at N=40 similar to the one at N=20. Using a large valence space, the neutron orbital 2d5/2 is shown to be a crucial ingredient for the interpretation of the nuclear structure at N≈40. The neutron 1g9/2-2d5/2 energy difference has been determined in 69Ni using the d(68Ni,p) transfer reaction in inverse kinematics. The experiment performed at GANIL used a 68Ni beam at 25.14 MeV/u seperated by the LISE3 spectrometer was impinging a CD2 target of 2.6 mg/cm2 thickness. The experimental setup consisted of CATS/MUST2-S1/EXOGAM detectors coupled to an ionization chamber and a plastic scintillator. The angular momenta and spectroscopic factors of the ground state (Jπ = 9/2+) and a doublet of states ( Jπ = 5/2+) around 2.48 MeV corresponding to the population of the 1g9/2 and the 2d5/2 orbitals, were obtained from the comparison between the experimental cross-sections as a function of the proton detection angle and ADWA calculations. The spins of the observed states were assigned by comparaison to large scale Shell-Model calculations. The position of the 2d5/2 orbital in 69Ni has been established for the first time. Our measurements support the hypothesis of a low-lying 2d5/2 orbital (≈2.5 MeV) with respect to the 1g9/2 neutron orbital and thus its major role in the structure of the nuclei around N=40., La fermeture de couche de l'oscillateur harmonique à N=40 dans le 68Ni est faible et perd sa rigidité après l'enlèvement (ou l'ajout) de paires de protons. Les calculs effectués dans cette région de masse prédisent un nouvel îlot d'inversion à N=40 semblable à celui à N=20 et montrant que le placement de l'orbital neutron 2d5/2 est un ingrédient essentiel pour l'interprétation de la structure nucléaire à N≈40. La différence d'énergie 1g9/2-2d5/2 a été déterminée dans le noyau 69Ni en utilisant la réaction de transfert d'un neutron d(68Ni,p) en cinématique inverse. L'expérience réalisée au GANIL utilisait un faisceau de 68Ni à 25,14 MeV/u. Les noyaux 68Ni séparés par le spectromètre LISE3 ont ensuite interagit avec une cible de CD2 d'épaisseur 2,6 mg/cm2. Le dispositif expérimental était composé principalement des détecteurs CATS/MUST2-S1/EXOGAM couplés à une chambre d'ionisation et un scintillateur plastique. Les moments angulaires et les facteurs spectroscopiques de l'état fondamental (Jπ = 9/2+) et d'un doublet d'états (Jπ = 5/2+) autour de 2,48 MeV, associés à la population des orbitales 1g9/2 et 2d5/2, ont été obtenus après la comparaison des sections efficaces différentielles et des calculs ADWA. Les spins des états observés ont été attribués après comparaison aux calculs de modèles en couches dans un grand espace de valence. La position de l'orbitale 2d5/2 dans 69Ni a été établie pour la première fois. Nos mesures confirment l'hypothèse de la faible différence d'énergie (≈2,5 MeV) entre l'orbitale neutron 2d5/2 et l'orbitale 1g9/2 et son importance pour décrire la structure des noyaux autour de N=40.

Physics at the drip-line offer the opportunity to study nuclei at the limits of the nuclear landscape, where additional protons or neutrons can no longer be kept in the nucleus. In the vicinity of the drip-lines, the structural features of the nuclei change with respect to the more stable nuclei, the normal shell closure of particles disappear and new phenomena appear, such as clusterization and halo. In this work we have revisited the spectroscopy of the unbound 10He by means of the 11 Li(d,3 He) reaction at 50 AMeV studied in missing mass method with the MUST2 array at the RIPS beam line of RIKEN. The experimental part of this study rely on new detection set-up using very thin silicon detectors. For the first time, the effective operability of these detectors, in conjunction with high granularity position sensitive detectors, was proved. The transfer reaction approach led to clear results on the 10He first resonant state position, found in this work at 1.4(3) MeV, in agreement with most of the previous experimental works. The extraction of a spectroscopic factor for the first time shed light on the overlap, found to be 0.13(6)., La physique à la drip-line offre l'opportunité d'étudier les noyaux à la limite du paysage couvert par la physique nucléaire, où l'addition de nouveaux protons et neutrons ne peut plus être supportée. A l'approche de la drip-line, la structure même des noyaux se trouve modifiée par rapport aux plus stables. Les fermetures de couches classiques disparaissent et de nouveaux phénomènes surgissent, tels que la clusterisation et les halos. Dans ce travail, nous avons revisité la spectroscopie du noyau non-lié 10He par l'intermédiaire d'une réaction de transfert d'un proton 11Li(d,3He) à 50 AMeV étudiée par la méthode de masse manquante. Pour ce faire, nous avons utilisé le détecteur MUST2 sur la ligne RIPS du RIKEN Nishina center. La partie expérimentale de ce travail repose sur un dispositif novateur utilisant des détecteurs de silicium très fins. Pour la première fois, la mise en oeuvre de ces derniers en conjonction avec des détecteurs sensibles en position de haute granularité a été démontrée. L'approche par réaction de transfert conduit à des résultats très clairs sur la position du premier état résonant du 10He, trouvé dans ce travail à 1.4(3) MeV, en accord avec la plupart des précédents travaux expérimentaux. L'obtention pour la première fois d'un facteur spectroscopique permet de nous renseigner sur la nature du recouvrement , trouvé égale à 0.13(6).