Search

Detailed spectroscopy of the neutron-deficient nucleus ^{36}Ca was obtained up to 9 MeV using the ^{37}Ca(p,d)^{36}Ca and the ^{38}Ca(p,t)^{36}Ca transfer reactions. The radioactive nuclei, produced by the LISE spectrometer at GANIL, interacted with the protons of the liquid hydrogen target CRYPTA, to produce light ejectiles (the deuteron d or triton t) that were detected in the MUST2 detector array, in coincidence with the heavy residues identified by a zero-degree detection system. Our main findings are (i) a similar shift in energy for the 1_{1}^{+} and 2_{1}^{+} states by about -250 keV, as compared with the mirror nucleus ^{36}S; (ii) the discovery of an intruder 0_{2}^{+} state at 2.83(13) MeV, which appears below the first 2^{+} state, in contradiction with the situation in ^{36}S; and (iii) a tentative 0_{3}^{+} state at 4.83(17) MeV, proposed to exhibit a bubble structure with two neutron vacancies in the 2s_{1/2} orbit. The inversion between the 0_{2}^{+} and 2_{1}^{+} states is due to the large mirror energy difference (MED) of -516(130) keV for the former. This feature is reproduced by shell model calculations, using the sd-pf valence space, predicting an almost pure intruder nature for the 0_{2}^{+} state, with two protons (neutrons) being excited across the Z=20 magic closure in ^{36}Ca (^{36}S). This mirror system has the largest MEDs ever observed, if one excludes the few cases induced by the effect of the continuum.

The $$^{27}\hbox {Al}(\hbox {p},\alpha )^{24}\hbox {Mg}$$ 27 Al ( p , α ) 24 Mg reaction, which drives the destruction of $$^{27}$$ 27 Al and the production of $$^{24}\hbox {Mg}$$ 24 Mg in stellar hydrogen burning, has been investigated via the Trojan Horse Method (THM), by measuring the $$^2\hbox {H}(^{27}\hbox {Al},\alpha ^{24}\hbox {Mg})\hbox {n}$$ 2 H ( 27 Al , α 24 Mg ) n three-body reaction. The experiment covered a broad energy range ($$E_\mathrm{c.m.}\le \,1.5\,\hbox {MeV}$$ E c . m . ≤ 1.5 MeV ), aiming to investigate those of interest for astrophysics. The results confirm the THM as a valuable technique for the experimental study of fusion reactions at very low energies and suggest the presence of a rich pattern of resonances in the energy region close to the Gamow window of stellar hydrogen burning (70–120 keV), with potential impact on astrophysics. To estimate such an impact a second run of the experiment is needed, since the background due the three-body reaction hampered to collect enough data to resolve the resonant structures and extract the reaction rate.

Background: It has been recently suggested that hydrogen ingestion into the helium shell of massive stars could lead to high C13 and N15 excesses when the shock of a core-collapse supernova passes through its helium shell. This prediction questions the origin of extremely high C13 and N15 abundances observed in rare presolar SiC grains which is usually attributed to classical novae. In this context the N13(α,p)O16 reaction plays an important role since it is in competition with N13β+ decay to C13. Purpose: The N13(α,p)O16 reaction rate used in stellar evolution calculations comes from the Caughlan and Fowler compilation with very scarce information on the origin of this rate and with no associated uncertainty. The goal of this work is to provide a recommended N13(α,p)O16 reaction rate, based on available experimental data, with a meaningful statistical uncertainty. Method: Unbound nuclear states in the F17 compound nucleus were studied using the spectroscopic information of the analog states in O17 nucleus that were measured at the Tandem-Alto facility using the C13(Li7,t)O17 α-particle-transfer reaction. The α-particle spectroscopic factors were derived using a finite-range distorted-wave Born approximation analysis. This spectroscopic information was used to calculate a recommended N13(α,p)O16 reaction rate with meaningful uncertainty using a Monte Carlo approach. Results: The N13(α,p)O16 reaction rate from the present work is found to be within a factor of two of the previous evaluation in the temperature range of interest, with a typical uncertainty of a factor ≈2-3. The source of this uncertainty has been identified to come from the three main contributing resonances at Erc.m.=221, 741, and 959 keV. This new error estimation translates to an overall uncertainty in the C13 production of a factor of 50 when using the lower and upper reaction rates in the conditions relevant for the N13(α,p)O16 activation. Conclusions: The main source of uncertainty on the re-evaluated N13(α,p)O16 reaction rate currently comes from the uncertain α-particle width of relevant F17 states.

Particle transfer reactions provide information on the single-particle structure of nuclei, with the caveat of imperfect reaction theory. In this paper, Bayesian analysis is applied in order to estimate the theoretical uncertainties associated with both the extraction of spectroscopic factors and the assignment of orbital angular momentum values from a pickup reaction. The authors find that these uncertainties are closely tied to experimental conditions, and discuss how to reduce their influence on future measurements.

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

The first investigation of the single-particle structure of the bound states of 17C, via the d(16C, p) transfer reaction, has been undertaken. The measured angular distributions confirm the spin-parity assignments of 1/2+ and 5/2+ for the excited states located at 217 and 335 keV, respectively. The spectroscopic factors deduced for these states exhibit a marked single-particle character, in agreement with shell model and particle-core model calculations, and combined with their near degeneracy in energy provide clear evidence for the absence of the N = 14 sub-shell closure. The very small spectroscopic factor found for the 3/2+ ground state is consistent with theoretical predictions and indicates that the {\nu}1d3/2 strength is carried by unbound states. With a dominant l = 0 valence neutron configuration and a very low separation energy, the 1/2+ excited state is a one-neutron halo candidate., Comment: 7 pages, 5 figures, Accepted for publication in Physics Letters B

The 12C + 12C fusion reaction plays a critical role in the evolution of massive stars and also strongly impacts various explosive astrophysical scenarios. The presence of resonances in this reaction at energies around and below the Coulomb barrier makes it impossible to carry out a simple extrapolation down to the Gamow window—the energy regime relevant to carbon burning in massive stars. The 12C + 12C system forms a unique laboratory for challenging the contemporary picture of deep sub-barrier fusion (possible sub-barrier hindrance) and its interplay with nuclear structure (sub-barrier resonances). Here, we show that direct measurements of the 12C + 12C fusion cross section may be made into the Gamow window using an advanced particle-gamma coincidence technique. The sensitivity of this technique effectively removes ambiguities in existing measurements made with gamma ray or charged-particle detection alone. The present cross-section data span over 8 orders of magnitude and support the fusion-hindrance model at deep sub-barrier energies.

Background: The Ne-22(alpha, n)Mg-25 reaction is an important source of neutrons for the s-process. Direct measurement of this reaction and the competing Ne-22(alpha,gamma)Mg-26 reaction are challenging due to the gaseous nature of both reactants, the low cross section and the experimental challenges of detecting neutrons and high-energy gamma rays. Detailed knowledge of the resonance properties enables the rates to be constrained for s-process models. Purpose: Previous experimental studies have demonstrated a lack of agreement in both the number and excitation energy of levels in Mg-26. To try to resolve the disagreement between different experiments, proton and deuteron inelastic scattering from Mg-26 have been used to identify excited states. Method: Proton and deuteron beams from the tandem accelerator at theMaier-Leibnitz Laboratorium at Garching, Munich, were incident upon enriched (MgO)-Mg-26 targets. Scattered particles were momentum-analyzed in the Q3D magnetic spectrograph and detected at the focal plane. Results: Reassignments of states around E-x = 10.8-10.83 MeV in Mg-26 suggested in previous works have been confirmed. In addition, new states in Mg-26 have been observed, two below and two above the neutron threshold. Up to six additional states above the neutron threshold may have been observed compared to experimental studies of neutron reactions on Mg-25, but some or all of these states may be due to Mg-24 contamination in the target. Finally, inconsistencies between measured resonance strengths and some previously accepted J(pi) assignments of excited Mg-26 states have been noted. Conclusion: There are still a large number of nuclear properties in Mg-26 that have yet to be determined and levels that are, at present, not included in calculations of the reaction rates. In addition, some inconsistencies between existing nuclear data exist that must be resolved in order for the reaction rates to be properly calculated.

The STELLA (STELlar LAboratory) experimental station for the measurement of deep sub-barrier light heavy-ion fusion cross sections has been installed at the Androm\`{e}de accelerator at the Institut de Physique Nucl\'{e}aire, Orsay (France). The setup is designed for the direct experimental determination of heavy-ion fusion cross sections as low as tens of picobarn. The detection concept is based on the coincident measurement of emitted gamma rays with the UK FATIMA (FAst TIMing Array) and evaporated charged particles using a silicon detector array. Key developments relevant to reaching the extreme sub-barrier fusion region are a rotating target mechanism to sustain beam intensities above 10$\mu$A, an ultra-high vacuum to prevent carbon built-up and gamma charged-particle timing in the order of nanoseconds sufficient to separate proton and alpha particles., Comment: 18 pages, 11 figures

Sulphur isotopic ratio measurements may help to establish the astrophysical sites in which certain presolar grains were formed. Nova model predictions of the S-34/S-32 ratio are, however, unreliable due to the lack of an experimental S-34(p,gamma)Cl-35 reaction rate. To this end, we have measured the S-34(He-3,d)Cl-35 reaction at 20 MeV using a high resolution quadrupole-dipole-dipole-dipolemagnetic spectrograph. Twenty-two levels over 6.2 MeV < E-x (Cl-35) < 7.4 MeV were identified, ten of which were previously unobserved. Proton-transfer spectroscopic factors have been measured for the first time over the energy range relevant for novae. With this new spectroscopic information a new S-34(p,gamma)Cl-35 reaction rate has been determined using a Monte Carlo method. Hydrodynamic nova model calculations have been performed using this new reaction rate. These models show that remaining uncertainties in the S-34(p,gamma) rate affect nucleosynthesis predictions by less than a factor of 1.4, and predict a S-34/S-32 isotopic ratio of 0.014-0.017. Since recent type II supernova models predict S-34/S-32 = 0.026-0.053, the S-34/S-32 isotopic ratio may be used, in conjunction with other isotopic signatures, to distinguish presolar grains from oxygen-neon nova and type II supernova origin. Our results address a key nuclear physics uncertainty on which recent considerations discounting the nova origin of several grains depend.

The direct component of the 60Fe(n,γ)61Fe cross section was investigated by populating the bound states of the 61Fe nucleus through the (d,pγ) transfer reaction in inverse kinematics using a radioactive beam of 60Fe at 27A MeV. The experiment was performed at GANIL using the MUST2 array and an annular double-sided silicon strip detector for the detection of the light charged particle in coincidence with the photons measured in the EXOGAM γ-ray detectors. For the first time, the spectroscopic factors of the first 3/2−, 5/2−, 1/2−, and 9/2+ states of 61Fe were deduced experimentally from an adiabatic distorted wave approximation analysis of the data. The obtained results show a very good agreement with the shell-model predictions. The calculated direct component of the (n,γ) cross section was found negligible and of about 2% of the total, indicating a dominant resonant component.

The 16-channel fast stretcher BaFPro module, originally developed for processing signals of Barium Fluoride scintillators, has been modified to make a high performing analog pulse-shape analysis of signals from the NE213 liquid scintillators of the EDEN neutron detector array. The module produces two Gaussian signals, whose amplitudes are proportional to the height of the fast component of the output light and to the total energy deposited into the scintillator, respectively. An in-beam test has been performed at INFN-LNS (Italy) demonstrating a low detection threshold, a good pulse-shape discrimination even at low energies and a wide dynamic range for the measurement of the neutrons energy.

In neutrinoless double-$\ensuremath{\beta}$ decay such as ${}^{136}$Xe to ${}^{136}$Ba, two neutrons become two protons, thus rearranging the occupancy of protons and neutrons in the ground states of the parent and daughter nuclei. From precision measurements of the cross sections of single-neutron adding and -removing reactions, the authors extract the change in ground-state neutron occupancies between ${}^{136}$Xe and ${}^{136}$Ba. Along with recent results on the proton occupancies, the new experimental neutron occupancies disagree with those used in existing theoretical calculations of the rate of this elusive $\ensuremath{\beta}$-decay mode, and provide a \hskip-0.22em \hskip-0.22embasis for improved estimates of the uncertainties for new calculations.

The measurement of gamma rays in the 0.3–30 MeV energy range with silicon detectors at room temperature via Compton scattering is being investigated for the next spatial gamma-ray observatory in the MeV band. In this contribution, we show that 60-keV gamma-ray detection with an energy resolution below 10 keV is possible using a 64×64 mm2, 1.5-mm thick, double-sided stripped silicon detector with a charge-sensitive preamplifier made of discrete commercial components. Our study of the noise including the bias circuit and the connection between the detector and the electronics allowed us to design a system able to sustain a leakage current of ∼50 nA/strip and a capacitance of ∼20 pF/strip. These results encourage us to investigate the use of integrated electronics in view of a satellite mission.

Astronomy in the MeV gamma-ray band (0.1 - 100 MeV) holds a rich promise for elucidating many fundamental questions concerning the most violent cosmic phenomena. The next generation of gamma-ray space instrument could be a Compton and pair-creation telescope made of two main parts: a silicon tracker optimized for Compton scattering of cosmic gamma rays and a calorimeter that absorbs the scattered photons. We present here the first results of GAMCOTE, a GAMma-ray COmpton TElescope prototype which includes thick double sided silicon strip detectors coupled to a LaBr3:Ce crystal read by a 64 multi-anode photomultiplier tube.

We have performed the $^{70}\mathrm{Zn}(d,^{3}\mathrm{He})^{69}\mathrm{Cu}$ proton pick-up reaction in direct kinematics using a deuteron beam at 27 MeV. The outgoing $^{3}\mathrm{He}$ particles were detected at the focal-plane detection system of an Enge split-pole spectrometer. The excitation-energy spectrum was reconstructed up to 7 MeV and spectroscopic factors were obtained after analysis of the angular distributions in the finite-range distorted-wave Born approximation. The results show three new angular distributions for which the $\ensuremath{\pi}{f}_{7/2}$ strength was measured and a lower limit of the centroid is established. State-of-the-art shell-model calculations are performed and predict a $\ensuremath{\pi}{f}_{7/2}$ strength that lies too high in energy in comparison to our experimental results.

The early E ⩽ 511 keV gamma-ray emission from novae depends critically on the F 18 ( p , α ) O 15 reaction. Unfortunately the reaction rate of the F 18 ( p , α ) O 15 reaction is still largely uncertain due to the unknown strengths of low-lying proton resonances near the F 18 + p threshold which play an important role in the nova temperature regime. We report here our last results concerning the study of the d ( F 18 , p ) F 19 ( α ) N 15 transfer reaction. We show in particular that these two low-lying resonances cannot be neglected. These results are then used to perform a careful study of the remaining uncertainties associated to the F 18 ( p , α ) O 15 and F 18 ( p , γ ) Ne 19 reaction rates.

Uncertainties in the thermonuclear rates of the $^{15}\text{O}(\ensuremath{\alpha},\ensuremath{\gamma}){}^{19}\text{Ne}$ and ${}^{18}\text{F}(p,\ensuremath{\alpha}){}^{15}\text{O}$ reactions affect model predictions of light curves from type I x-ray bursts and the amount of the observable radioisotope $^{18}\text{F}$ produced in classical novae, respectively. To address these uncertainties, we have studied the nuclear structure of $^{19}\text{Ne}$ over ${E}_{x}=4.0\ensuremath{-}5.1$ and 6.1--7.3 MeV using the $^{19}\text{F}(^{3}\text{He},t)^{19}\text{Ne}$ reaction. We find the ${J}^{\ensuremath{\pi}}$ values of the 4.14- and 4.20-MeV levels to be consistent with $9/{2}^{\ensuremath{-}}$ and $7/{2}^{\ensuremath{-}}$, respectively, in contrast to previous assumptions. We confirm the recently observed triplet of states around 6.4 MeV and find evidence that the state at 6.29 MeV, just below the proton threshold, is either broad or a doublet. Our data also suggest that predicted but yet unobserved levels may exist near the 6.86-MeV state. Higher resolution experiments are urgently needed to further clarify the structure of $^{19}\text{Ne}$ around the proton threshold before a reliable ${}^{18}\text{F}(p,\ensuremath{\alpha}){}^{15}\text{O}$ rate for nova models can be determined.

26Al is an important radioisotope in astrophysics that provides evidence of ongoing nucleosynthesis in the Galaxy. The 23Na(α, p)26Mg reaction has been identified by a sensitivity study as being one of the most important reactions for the production of 26Al in the convective C/Ne burning shell of massive stars. Owing to large uncertainties in previous experimental data, model calculations are used for the reaction rate of 23Na(α, p)26Mg in this sensitivity study. Current experimental data suggest a reaction rate a factor of ∼40 higher than model calculations. However, a new measurement of this reaction cross section has been made in inverse kinematics in the energy range E(c.m.)=1.28-3.15 MeV at TRIUMF, and found to be in reasonable agreement with the model calculation. A new reaction rate is calculated and tight constraints on the uncertainty in the production of 26Al, due to this reaction, are determined.

26Al is an important radioisotope in astrophysics that provides evidence of ongoing nucleosynthesis in the Galaxy. The 23Na(α, p)26Mg reaction has been identified by a sensitivity study as being one of the most important reactions for the production of 26Al in the convective C/Ne burning shell of massive stars. Owing to large uncertainties in previous experimental data, model calculations are used for the reaction rate of 23Na(α, p)26Mg in this sensitivity study. Current experimental data suggest a reaction rate a factor of ∼40 higher than model calculations. However, a new measurement of this reaction cross section has been made in inverse kinematics in the energy range E(c.m.)=1.28-3.15 MeV at TRIUMF, and found to be in reasonable agreement with the model calculation. A new reaction rate is calculated and tight constraints on the uncertainty in the production of 26Al, due to this reaction, are determined.

The 7Be + p elastic cross section has been measured at the Centre de Recherches du Cyclotron RIB facility at Louvain-la-Neuve in the c.m. energy region from 0.3 to 0.75 MeV by bombarding a proton-rich target with a radioactive 7Be beam. The recoil protons have been detected in the angular range θc.m. = 120.2° − 131.1° and θc.m. = 156.6° − 170.2° using the LEDA system. From a R-matrix analysis of the cross section data, we extract the energy and the width of the 1+ resonance. The scattering lengths α01 = 25 ± 9 fm (channel spin I = 1) and α02 = −7 ± 3 fm (channel spin I = 2) are deduced. Implications on the low energy S-factor of the 7Be(p, γ)8B reaction are discussed.

The 7 Be+p elastic cross section has been measured at the Centre de Recherches du Cyclotron RIB facility at Louvain-la-Neuve in the c.m. energy region from 0.3 to 0.75 MeV by bombarding a proton-rich target with a radioactive 7 Be beam. The recoil protons have been detected in the angular range θc.m.=120.2°–131.1° and θc.m.=156.6°–170.2° using the LEDA system. From a R-matrix analysis of the cross section data, we obtain the energy and the width of the 1+ resonance (Ex=0.77 MeV). The l=0 scattering lengths a01=25±9 fm (channel spin I=1) and a02=−7±3 fm (channel spin I=2) have been deduced. They are compared to values expected from charge-symmetry properties. Implications on the low energy S-factor of the 7 Be(p, γ) 8 B reaction are discussed.

International audience; Novae are astrophysical events (violent explosion) occurring in close binary systems consisting of a white dwarf and a main-sequence star or a star in a more advanced stage of evolution.They are called "narrow systems" because the two components interact with each other: there is a process of mass exchange with resulting in the transfer of matter from the companion star to the white dwarf, leading to the formation of this last of the so-called accretion disk, rich mainly of hydrogen.Over time, more and more material accumulates until the pressure and the temperature reached are sufficient to trigger nuclear fusion reactions, rapidly converting a large part of the hydrogen into heavier elements. The products of "hot hydrogen burning" are then placed in the interstellar medium as a result of violent explosions.Studies on the element abundances observed in these events can provide important information about the stages of evolution stellar.During the outbursts of novae some radioactive isotopes are synthesized: in particular, the decay of short-lived nuclei such as N-13 and F-18 with subsequent emission of gamma radiation energy below 511 keV. The gamma rays from products electron-positron annihilation of positrons emitted in the decay of F-18 are the most abundant and the first observable as soon as the atmosphere of the nova starts to become transparent to gamma radiation. Hence the importance of the study of nuclear reactions that lead both to the formation and to the destruction of F-18. Among these, the F-18(p, alpha)O-15 reaction is one of the main channels of destruction. This reaction was then studied at energies of astrophysical interest.The experiment done at Riken, Japan, has as its objective the study of the F-18(p, alpha)O-15 reaction, using a beam of F-18 produced at CRIB, to derive important information about the phenomenon of novae.In tis paper we present the experimental technique and the Monte Carlo code developed to be used in the data analysis process.

The response of a scintillation detector with a cylindrical 1.5-inch LaBr3:Ce crystal to incident neutrons has been measured in the energy range En = 2-12 MeV. Neutrons were produced by proton irradiation of a Li target at Ep = 5-14.6 MeV with pulsed proton beams. Using the time-of-flight information between target and detector, energy spectra of the LaBr3:Ce detector resulting from fast neutron interactions have been obtained at 4 different neutron energies. Neutron-induced gamma rays emitted by the LaBr3:Ce crystal were also measured in a nearby Ge detector at the lowest proton beam energy. In addition, we obtained data for neutron irradiation of a large-volume high-purity Ge detector and of a NE-213 liquid scintillator detector, both serving as monitor detectors in the experiment. Monte-Carlo type simulations for neutron interactions in the liquid scintillator, the Ge and LaBr3:Ce crystals have been performed and compared with measured data. Good agreement being obtained with the data, we present the results of simulations to predict the response of LaBr3:Ce detectors for a range of crystal sizes to neutron irradiation in the energy range En = 0.5-10 MeV, Comment: 28 pages, 10 figures, 4 Tables

International audience; The O-17(p,alpha)N-14 reaction is of paramount importance for the nucleosynthesis in a number of stellar sites, including red giants (RG), asymptotic giant branch (AGB) stars, massive stars and classical novae. We report on the indirect study of the O-17(p,alpha)N-14 reaction via the Trojan Horse Method by applying the approach recently developed for extracting the resonance strength of the narrow resonance at E-c.m.(R) = 65 keV (E-X = 5.673 MeV). The strength of the 65 keV resonance in the O-17(p,alpha)N-14 reaction, measured by means of the THM, has been used to renormalize the corresponding resonance strength in the O-17 + p radiative capture channel.

We will present measurements and modeling for two aspects of the CnN+ - He collisions (n=1-3, v=2.25 a.u) :cross sections for electronic excitation processes and fragmentation branching ratios for the excited and ionized CnNq+ molecules produced in the collision (q=-1,0,1,2-5)., SCOPUS: cp.j, info:eu-repo/semantics/published

The ${}^{26}\mathrm{Al}$ radioisotope is of great importance for understanding the chemical and dynamical evolution of our galaxy. Among the possible stellar sources, massive stars are believed to be the main producer of this radioisotope. Understanding ${}^{26}\mathrm{Al}$ nucleosynthesis in massive stars requires estimates of the thermonuclear reaction rates of the $^{26}\mathrm{Al}$${(n,p)}^{26}$Mg, $^{26}\mathrm{Al}$${(n,\ensuremath{\alpha})}^{23}$Na, and $^{23}\mathrm{Na}$${(\ensuremath{\alpha},p)}^{26}$Mg reactions. These reaction rates depend on the spectroscopic properties of ${}^{27}\mathrm{Al}$ states above the neutron and alpha thresholds. In this context, the $^{27}\mathrm{Al}$${(p,{p}^{\ensuremath{'}})}^{27}$Al* reaction was studied at 18 MeV using a high-resolution Enge Split-Pole spectrometer. States from the ground state up to excitation energies of $\ensuremath{\approx}$14 MeV were populated. While up to the ${}^{23}\mathrm{Na}$ + $\ensuremath{\alpha}$ threshold no additional states are observed, we report for the first time 30 new levels above the ${}^{23}\mathrm{Na}$ + $\ensuremath{\alpha}$ threshold and more than 30 new states above the ${}^{26}\mathrm{Al}$ + n threshold for which excitation energies are determined with an uncertainty of 4--5 keV.

The indirect measurement of 17O(p,α)14N cross section was performed by means of the Trojan Horse Method. This approach allowed to investigate the ultra-low energy range ( E c . m . = 0 − 300 keV ) relevant for several astrophysics environments, where two resonant levels of 18F at E c . m . R = 65 keV and E c . m . R = 183 keV play a significant role in the reaction rate determination.

The 17O(p,α)14N reaction is of paramount importance for the nucleosynthesis in a number of stellar sites, including red giants (RG), asymptotic giant branch (AGB) stars, massive stars and classical novae. We report on the indirect study of the 17O(p,α)14N reaction via the Trojan Horse Method by applying the approach recently developed for extracting the resonance strength of narrow resonance in the ultra-low energy region.

International audience; The experimental setup STELLA (STELlar LAboratory) is designed for the measurement of deep sub-barrier light heavy ion fusion cross sections. For background suppression the γ-particle coincidence technique is used. In this project, LaBr3 detectors from the UK FATIMA (FAst TIMing Array) collaboration are combined with annular silicon strip detectors customized at IPHC-CNRS, Strasbourg, and the setup is located at Andromède, IPN, Orsay. The commissioning of the experimental approach as well as a sub-barrier 12C +12C → 24Mg∗ cross section measurement campaign are carried out.

International audience; The neutron decay of the resonant states of light neutron-rich nuclei is an important and poorly explored property, useful to extract valuable nuclear structure information. The neutron decay of the (15)C resonances populated via the two-neutron transfer reaction (13)C((18)O,(16)O n) at 84 MeV incident energy is studied using an innovative technique which couples the MAGNEX magnetic spectrometer and the EDEN neutron detector array. The data show that the recently observed (15)C Giant Pairing Vibration at 13.7 MeV mainly decays via two-neutron emission.

The abundance of 18F in Nova explosions is an important issue for the understanding of this astrophysical phenomenon. For this reason it is necessary to study the nuclear reactions that produce or destroy this isotope in novae. Among these latter processes, the 18F(p,α)15O is one of the main 18F destruction channels. We report here on the preliminary results of the first experiment that applies the Trojan Horse Method to a Radioactive Ion Beam induced reaction. The experiment was performed using the CRIB apparatus of the Center for Nuclear Study of The Tokyo University.

This is the publisher's version, also available electronically from http://journals.aps.org/prc/abstract/10.1103/PhysRevC.84.011301.

$\ensuremath{\gamma}$-ray production cross sections have been measured in proton irradiations of N, Ne, and Si and $\ensuremath{\alpha}$-particle irradiations of N and Ne. In the same experiment we extracted also line shapes for strong $\ensuremath{\gamma}$-ray lines of $^{16}\mathrm{O}$ produced in proton and $\ensuremath{\alpha}$-particle irradiations of O. For the measurements gas targets were used for N, O, and Ne and a thick foil for Si. All targets were of natural isotopic composition. Beams in the energy range up to 26 MeV for protons and 39 MeV for $\ensuremath{\alpha}$ particles were delivered by the Institut de Physique Nucl\'eaire--Orsay tandem accelerator. The $\ensuremath{\gamma}$ rays were detected with four high-purity Ge detectors in the angular range ${30}^{\ifmmode^\circ\else\textdegree\fi{}}$ to ${135}^{\ifmmode^\circ\else\textdegree\fi{}}$. We extracted 36 cross-section excitation functions for proton reactions and 14 for $\ensuremath{\alpha}$-particle reactions. For the majority of the excitation functions no other data exist to our knowledge. Where comparison with existing data was possible, usually a very good agreement was found. It is shown that these data are very interesting for constraining nuclear reaction models. In particular, the agreement of cross section calculations in the nuclear reaction code talys with the measured data could be improved by adjusting the coupling schemes of collective levels in the target nuclei $^{14}\mathrm{N}$, $^{20,22}\mathrm{Ne}$, and $^{28}\mathrm{Si}$. The importance of these results for the modeling of nuclear $\ensuremath{\gamma}$-ray line emission in astrophysical sites is discussed.

The {sup 17}O(p,{alpha}){sup 14}N reaction is of fundamental relevance in several astrophysical scenarios, such as novae, asymptotic giant branch nucleosynthesis, and {gamma}-ray astronomy. We report on the indirect measurement of the {sup 17}O(p,{alpha}){sup 14}N reaction bare-nucleus cross section in the low-energy region. In particular, the two resonances at E{sub R}{sup c.m.}=65 keV and E{sub R}{sup c.m.}=183 keV, which dominate the reaction rate inside the Gamow window, have been observed, and the strength of the 65 keV resonance has been deduced. The reaction rate determination and the comparison with the results of the previous measurements are also discussed.

INTEGRAL and RHESSI spacecrafts recently detected the 1.173 and 1.333 MeV γ‐ray lines coming from the 60Fe—60Co—60Ni radioactive decay chain. The long lived isotope 60Fe (T1/2 = 1.5 106y) is believed to be primarily produced in core‐collapse supernovae. However the interpretation of the observations is difficult because of the large uncertainties concerning 59Fe(n,γ)60Fe and 60Fe(n,γ)61Fe cross sections, involved in 60Fe nucleosynthesis.The direct component of the 60Fe(n,γ)61Fe reaction was studied indirectly via the d(60Fe,pγ)61Fe transfer reaction. The experiment performed in GANIL in spring 2009 will allow to determine the excitation energies of the populated excited states of 61Fe and for the first time their spectroscopic factors as well as their transfer angular momentum.I will first give an overview of the astrophysical context, then I will describe the experimental setup and finally present some preliminary results of the ongoing analysis.

$\ensuremath{\gamma}$-rays following the $\ensuremath{\beta}$ and $\ensuremath{\beta}\text{\ensuremath{-}}n$ decays of the very neutron rich ${}_{31}^{84}{\mathrm{Ga}}_{53}$ produced by the photofission of $^{238}\mathrm{U}$ have been studied at the newly built ISOL facility of IPN Orsay: ALTO. Two activities were observed and assigned to two $\ensuremath{\beta}$-decaying states: $^{84}\mathrm{Ga}$${}^{g}$, ${I}^{\ensuremath{\pi}}=({0}^{\ensuremath{-}})$ and $^{84}\mathrm{Ga}$${}^{m}$, ${I}^{\ensuremath{\pi}}=({3}^{\ensuremath{-}},{4}^{\ensuremath{-}})$. Excitation energies of the ${2}_{1}^{+}$ and ${4}_{1}^{+}$ states of ${}_{32}^{84}{\mathrm{Ge}}_{52}$ were measured at $E({2}_{1}^{+})=624.3$ keV and $E({4}_{1}^{+})=1670.1$ keV. Comparison with HFB $+$ GCM calculations allows to establish the collective character of this nucleus. The excitation energy of the $1/{2}_{1}^{+}$ state in ${}_{32}^{83}{\mathrm{Ga}}_{51}$ known to carry a large part of the neutron $3{s}_{1/2}$ strength was measured at $247.8$ keV. Altogether these data allow to confirm the new single particle state ordering which appears immediately after the double $Z=28$ and $N=50$ shell closure and to designate $^{78}\mathrm{Ni}$ as a fragile and easily polarized doubly-magic core.

An excited state in the proton-rich unbound nucleus $^{12}\mathrm{O}$ was identified at 1.8(4) MeV via missing-mass spectroscopy with the $^{14}\mathrm{O}(p,t)$ reaction at $51\text{ }\text{ }A\mathrm{MeV}$. The spin-parity of the state was determined to be ${0}^{+}$ or ${2}^{+}$ by comparing the measured differential cross sections with distorted-wave calculations. The lowered location of the excited state in $^{12}\mathrm{O}$ indicates the breakdown of the major shell closure at $Z=8$ near the proton drip line. This demonstrates the persistence of mirror symmetry in the disappearance of the magic number 8 between $^{12}\mathrm{O}$ and its mirror partner $^{12}\mathrm{Be}$.

An excited state in the proton-rich unbound nucleus 12O was identified at 1.8(4) MeV via missing-mass spectroscopy with the 14O(p,t) reaction at 51 AMeV. The spin-parity of the state was determined to be 0+ or 2+ by comparing the measured differential cross sections with distorted-wave calculations. The lowered location of the excited state in 12O indicates the breakdown of the major shell closure at Z=8 near the proton drip line. This demonstrates the persistence of mirror symmetry in the disappearance of the magic number 8 between 12O and its mirror partner 12Be.

Six proton-emitting states in $^{19}\mathrm{Ne}$ were studied through the inelastic scattering reaction $\mathrm{H}(^{19}\mathrm{Ne},p)^{19}\mathrm{Ne}^{*}(p)^{18}\mathrm{F}$. Their energies and widths were derived from the protons detected at zero degree, while proton-proton angular correlations between the detector at zero degree and a segmented annular detector were used to determine their spin value. In addition to the known states, a new broad $J=\frac{1}{2}$ resonance has been evidenced at ${E}_{x}\ensuremath{\approx}7.9\text{ }\text{ }\mathrm{MeV}$, $\ensuremath{\approx}1.45\text{ }\text{ }\mathrm{MeV}$ above the proton emission threshold. By introducing this resonance, the $^{18}\mathrm{F}(p,\ensuremath{\alpha})^{15}\mathrm{O}$ destruction rate in novae is significantly enhanced. This reduces the chance to observe the cosmic $\ensuremath{\gamma}$-ray emission of $^{18}\mathrm{F}$ from novae in space telescopes.

The nucleosynthetic origin of $^{26}\mathrm{Al}$ (${t}_{1/2}=0.72$ Myr) in the early solar system is still an open question. Several models predict that short-lived radionuclides could be produced by irradiation of circumsolar material by light charged particles emitted by the young sun. Within some models, most of the $^{26}\mathrm{Al}$ is produced by $^{3}\mathrm{He}$-induced reactions on $^{24}\mathrm{Mg}$. Little experimental data exist on $^{3}\mathrm{He}$ reactions so that irradiation models have had to rely on theoretical cross sections deduced from statistical nuclear reaction codes. We performed a direct measurement of the $^{26}\mathrm{Al}$ production on Mg target by means of $\ensuremath{\gamma}$ ray spectroscopy and accelerator mass spectrometry (AMS). The data indicate that the theoretical cross section used in previous approaches was overestimated by a factor of 3. Taking the particle spectra considered in theoretical approaches these data lead to a net reduction of the $^{26}\mathrm{Al}$ production of a factor of 2. We calculated the relative contribution of the different $^{26}\mathrm{Al}$ production channels depending on the irradiation scenario. We show that extremely large particles fluxes would be necessary to reach the canonical ${}^{26}\mathrm{Al}{/}^{27}\mathrm{Al}$ $=5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ in solids that were present in the early solar system. An in situ origin of this important isotopic chronometer by irradiation is unlikely.

Because of the still present uncertainties on its rate, the 17O(p,α)14N is one of the most important reaction to be studied in order to get more information about the fate of 17O in different astrophysical scenarios. The preliminary study of the three‐body reaction 2H(17O,α14N)n is presented here as a first stage of the indirect study of this important 17O(p,α)14N reaction through the Trojan Horse Method (THM)

{gamma}-ray production cross sections for proton and {alpha}-particle interactions with {sup 12}C, {sup 16}O, {sup 24}Mg, and Fe have been measured in the energy range 5-25 MeV with proton beams and 5-40 MeV with {alpha}-particle beams. Isotopically pure foils of {sup 24}Mg and foils of natural isotopical composition of C, MgO, and Fe have been used. {gamma}-ray angular distributions were obtained with five high-purity Ge detectors with bismuth germanate Compton shields placed at angles of 45 deg. to 157.5 deg. Cross sections for more than 50 different {gamma}-ray transitions were extracted, and for many of them no data have been published before. Comparison of present data with data available in the literature shows mostly good to excellent agreement. In addition to the production cross sections, high-statistics, low-background line shapes of the 4.438 MeV {sup 12}C {gamma} ray from inelastic scattering off {sup 12}C and spallation of {sup 16}O were obtained. Comparison with nuclear reaction calculations shows that these data place interesting constraints on nuclear reaction models.