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The nature of the 1 − and 2 − excited states in Be 10 is studied using the Be 11 ( p , d ) transfer reaction in inverse kinematics at 10A MeV at TRIUMF ISAC-II, in particular to assess whether either of them can be considered as an excited halo state. The angular distributions for both states are extracted using deuteron- γ coincidences and analyzed using a transfer model taking into account one-step and two-step processes. A good fit of the angular distributions is obtained considering only the one-step process, whereby an inner p 3 / 2 neutron of Be 11 is removed, leaving the halo neutron intact. Higher-order processes however cannot be rejected. The small spectroscopic factors extracted suggest that the structure of both states is not uniquely halo-like, but rather display a more complex configuration mixing cluster and halo structures. Further insights are limited, as this experiment specifically probed the halo-like (but not cluster-like) Be 11 ( 1 / 2 + ) ⊗ ( ν p 3 / 2 ) − 1 configuration in both states.

Background: Globular clusters are known to exhibit anomalous abundance trends such as the sodium-oxygen anticorrelation. This trend is thought to arise via pollution of the cluster interstellar medium from a previous generation of stars. Intermediate-mass asymptotic giant branch stars undergoing hot bottom burning (HBB) are a prime candidate for producing sodium-rich oxygen-poor material, and then expelling this material via strong stellar winds. The amount of $^{23}\mathrm{Na}$ produced in this environment has been shown to be sensitive to uncertainties in the $^{22}\mathrm{Ne}(p,\ensuremath{\gamma})^{23}\mathrm{Na}$ reaction rate. The $^{22}\mathrm{Ne}(p,\ensuremath{\gamma})^{23}\mathrm{Na}$ reaction is also activated in classical nova nucleosynthesis, strongly influencing predicted isotopic abundance ratios in the Na-Al region. Therefore, improved nuclear physics uncertainties for this reaction rate are of critical importance for the identification and classification of pre-solar grains produced by classical novae.Purpose: At temperatures relevant for both HBB in AGB stars and classical nova nucleosynthesis, the $^{22}\mathrm{Ne}(p,\ensuremath{\gamma})^{23}\mathrm{Na}$ reaction rate is dominated by narrow resonances, with additional contribution from direct capture. This study presents new strength values for seven resonances, as well as a study of direct capture.Method: The experiment was performed in inverse kinematics by impinging an intense isotopically pure beam of $^{22}\mathrm{Ne}$ onto a windowless ${\mathrm{H}}_{2}$ gas target. The $^{23}\mathrm{Na}$ recoils and prompt $\ensuremath{\gamma}$ rays were detected in coincidence using a recoil mass separator coupled to a $4\ensuremath{\pi}$ bismuth-germanate scintillator array surrounding the target.Results: For the low-energy resonances, located at center of mass energies of 149, 181, and 248 keV, we recover stength values of $\ensuremath{\omega}{\ensuremath{\gamma}}_{149}=0.{17}_{\ensuremath{-}0.04}^{+0.05}, \ensuremath{\omega}{\ensuremath{\gamma}}_{181}=2.2\ifmmode\pm\else\textpm\fi{}0.4$, and $\ensuremath{\omega}{\ensuremath{\gamma}}_{248}=8.2\ifmmode\pm\else\textpm\fi{}0.7 \ensuremath{\mu}\text{eV}$, respectively. These results are in broad agreement with recent studies performed by the LUNA and TUNL groups. However, for the important reference resonance at 458 keV we obtain a strength value of $\ensuremath{\omega}{\ensuremath{\gamma}}_{458}=0.44\ifmmode\pm\else\textpm\fi{}0.02$ eV, which is significantly lower than recently reported values. This is the first time that this resonance has been studied completely independently from other resonance strengths. For the 632-keV resonance we recover a strength value of $\ensuremath{\omega}{\ensuremath{\gamma}}_{632}=0.48\ifmmode\pm\else\textpm\fi{}0.02$ eV, which is an order of magnitude higher than a recent study. For reference resonances at 610- and 1222-keV, our strength values are in agreement with the literature. In the case of direct capture, we recover an $S$ factor of 60 keV b, consistent with prior forward kinematics experiments.Conclusions: In summary, we have performed the first direct measurement of $^{22}\mathrm{Ne}(p,\ensuremath{\gamma})^{23}\mathrm{Na}$ in inverse kinematics. Our results are in broad agreement with the literature, with the notable exception of the 458-keV resonance, for which we obtain a lower strength value. We assessed the impact of the present reaction rate in reference to a variety of astrophysical environments, including AGB stars and classical novae. Production of $^{23}\mathrm{Na}$ in AGB stars is minimally influenced by the factor of 4 increase in the present rate compared to the STARLIB-2013 compilation. The present rate does however impact upon the production of nuclei in the Ne-Al region for classical novae, with dramatically improved uncertainties in the predicted isotopic abundances present in the novae ejecta.

Angular distributions of the elastic, inelastic, and breakup cross sections of the halo nucleus ^{11}Be on ^{197}Au were measured at energies below (E_{lab}=31.9 MeV) and around (39.6 MeV) the Coulomb barrier. These three channels were unambiguously separated for the first time for reactions of ^{11}Be on a high-Z target at low energies. The experiment was performed at TRIUMF (Vancouver, Canada). The differential cross sections were compared with three different calculations: semiclassical, inert-core continuum-coupled-channels and continuum-coupled-channels ones with including core deformation. These results show conclusively that the elastic and inelastic differential cross sections can only be accounted for if core-excited admixtures are taken into account. The cross sections for these channels strongly depend on the B(E1) distribution in ^{11}Be, and the reaction mechanism is sensitive to the entanglement of core and halo degrees of freedom in ^{11}Be.

Background: The rate of the F18(p,γ)Ne19 reaction affects the final abundance of the radioisotope F18 ejected from novae. This nucleus is important as its abundance is thought to significantly influence the first-stage 511-keV and continuum γ-ray emission in the aftermath of novae. No successful measurement of this reaction existed prior to this work, and the rate used in stellar models had been calculated based on incomplete information from contributing resonances. Purpose: Of the two resonances thought to provide a significant contribution to the astrophysical reaction rate, located at Ec.m.=330 and 665 keV, the former has a radiative width estimated from the assumed analog state in the mirror nucleus, F19, while the latter resonance does not have an analog state assignment, resulting in an arbitrary radiative width being assumed. As such, a direct measurement was needed to establish what role this resonance plays in the destruction of F18 at nova temperatures. This paper extends and takes the place of a previous Letter which reported the strength of the Ec.m.=665 keV resonance. Method: The DRAGON recoil separator was used to directly measure the strength of the important 665-keV resonance in this reaction, in inverse kinematics, by observing Ne19 reaction products. A radioactive F18 beam was provided by the ISAC facility at TRIUMF. R-matrix calculations were subsequently used to evaluate the significance of the results at astrophysical energies. Results: We report the direct measurement of the F18(p,γ)Ne19 reaction with the reevaluation of several detector efficiencies and the use of an updated Ne19 level scheme in the reaction rate analysis. The strength of the 665-keV resonance (Ex=7.076 MeV) is found to be an order of magnitude weaker than currently assumed in nova models. An improved analysis of the previously reported data is presented here, resulting in a slightly different value for the resonance strength. These small changes, however, do not alter the primary conclusions. Conclusions: Reaction rate calculations definitively show that the 665-keV resonance plays no significant role in the destruction of F18 at nova temperatures.

The DRAGON facility for the study of radiative capture reactions has an extended gas target, surrounded by an array of BGO detectors. The distribution of detected gamma rays amongst the segmented array permits an estimate of the reaction position and consequently of the resonance energy. We report a study of the technique, using the 24 Mg(p, γ ) 25 Al reaction. Energy determination to better than 0.5% has been demonstrated.

This work reports on the scattering of 11Be on 197Au at energies around and below the Coulomb barrier. By experimentally identifying the elastic scattering, inelastic scattering and breakup channels, and comparing them with different calculations, valuable information on the 11Be structure and its B(E1) distribution to the continuum are obtained. On top of that, a deeper understanding of the scattering process at low energies is achieved for reactions of this kind, making these studies extendable to other loosely-bound systems like 17,19C Gobierno de España FPA2015-64969-P, FIS2014-53448-C2-1-P, FPA2013-47327-c02-01-R, FPA2012-32443, FIS2013-41994-P, CSD2007-00042 EUROCORES EUI-2009-04162 European Union 654002

At low stellar temperatures the energy release due to the CN cycle is regulated by its slowest reaction ${}^{14}\mathrm{N}(p,\ensuremath{\gamma}){}^{15}\mathrm{O}$, the rate of which strongly depends on the subthreshold resonance at ${E}_{\mathrm{c}}.\mathrm{m}.=\ensuremath{-}504\phantom{\rule{0.28em}{0ex}}\mathrm{keV}$, which corresponds to the 6.79 MeV state in ${}^{15}\mathrm{O}$. By using the Doppler-shift attenuation method and the ${}^{3}\mathrm{He}({}^{16}\mathrm{O},\ensuremath{\alpha}){}^{15}\mathrm{O}$ reaction to populate the state, we obtained an upper limit on the lifetime of this state of $\ensuremath{\tau}l1.8\phantom{\rule{0.28em}{0ex}}\mathrm{fs}$ [68.3% confidence level (C.L.)]. In addition we measured the lifetimes of the 6.18 and 6.86 MeV states to be $\ensuremath{\tau}l2.5$ and $\ensuremath{\tau}=13.{3}_{\ensuremath{-}1.2}^{+0.9}\phantom{\rule{0.28em}{0ex}}\mathrm{fs}$, respectively (68.3% C.L.), in good agreement with the literature.

The reaction mechanisms of the two-neutron transfer reaction ${}^{12}$C(${}^{6}$He,${}^{4}$He) have been studied at ${E}_{\mathrm{lab}}=30$ MeV at the TRIUMF ISAC-II facility using the Silicon Highly-segmented Array for Reactions and Coulex (SHARC) charged-particle detector array. Optical potential parameters have been extracted from the analysis of the elastic scattering angular distribution. The new potential has been applied to the study of the transfer angular distribution to the 2${}_{2}^{+}$ 8.32 MeV state in ${}^{14}$C, using a realistic three-body ${}^{6}$He model and advanced shell-model calculations for the carbon structure, allowing to calculate the relative contributions of the simultaneous and sequential two-neutron transfer. The reaction model provides a good description of the 30-MeV data set and shows that the simultaneous process is the dominant transfer mechanism. Sensitivity tests of optical potential parameters show that the final results can be considerably affected by the choice of optical potentials. A reanalysis of data measured previously at ${E}_{\mathrm{lab}}=18$ MeV, however, is not as well described by the same reaction model, suggesting that one needs to include higher-order effects in the reaction mechanism.

The ${}^{33}$S($p,\ensuremath{\gamma}$)${}^{34}$Cl reaction is important for constraining predictions of certain isotopic abundances in oxygen-neon novae. Models currently predict as much as 150 times the solar abundance of ${}^{33}$S in oxygen-neon nova ejecta. This overproduction factor may vary by orders of magnitude due to uncertainties in the ${}^{33}$S($p,\ensuremath{\gamma}$)${}^{34}$Cl reaction rate at nova peak temperatures. Depending on this rate, ${}^{33}$S could potentially be used as a diagnostic tool for classifying certain types of presolar grains. Better knowledge of the ${}^{33}$S($p,\ensuremath{\gamma}$)${}^{34}$Cl rate would also aid in interpreting nova observations over the S-Ca mass region and contribute to the firm establishment of the maximum endpoint of nova nucleosynthesis. Additionally, the total S elemental abundance which is affected by this reaction has been proposed as a thermometer to study the peak temperatures of novae. Previously, the ${}^{33}$S($p,\ensuremath{\gamma}$)${}^{34}$Cl reaction rate had only been studied directly down to resonance energies of 432 keV. However, for nova peak temperatures of $0.2--0.4$ GK there are seven known states in ${}^{34}$Cl both below the 432-keV resonance and within the Gamow window that could play a dominant role. Direct measurements of the resonance strengths of these states were performed using the DRAGON (Detector of Recoils And Gammas of Nuclear reactions) recoil separator at TRIUMF. Additionally two new states within this energy region are reported. Several hydrodynamic simulations have been performed, using all available experimental information for the ${}^{33}$S($p,\ensuremath{\gamma}$)${}^{34}$Cl rate, to explore the impact of the remaining uncertainty in this rate on nucleosynthesis in nova explosions. These calculations give a range of $\ensuremath{\approx}$20--150 for the expected ${}^{33}$S overproduction factor, and a range of $\ensuremath{\approx}$100--450 for the ${}^{32}$S/${}^{33}$S ratio expected in ONe novae.

The rate of the 18F(p,γ)19Ne reaction affects the final abundance of the γ-ray observable radioisotope 18F, produced in novae. However, no successful measurement of this reaction exists and the rate used is calculated from incomplete information on the contributing resonances. Of the two resonances thought to play a significant role, one has a radiative width estimated from the assumed analogue state in the mirror nucleus, 19F. The second does not have an analogue state assignment at all, resulting in an arbitrary radiative width being assumed. Here, we report the first successful direct measurement of the 18F(p,γ)^19Ne reaction. The strength of the 665 keV resonance (Ex=7.076 MeV) is found to be over an order of magnitude weaker than currently assumed in nova models. Reaction rate calculations show that this resonance therefore plays no significant role in the destruction of ^{18}F at any astrophysical energy.

The $\ensuremath{\beta}$-feeding probabilities for three important contributors to the decay heat in nuclear reactors, namely ${}^{102,104,105}$Tc, have been measured using the total absorption spectroscopy technique. For the measurements, sources of very high isobaric purity have been obtained using a Penning trap (JYFLTRAP). A detailed description of the data analysis is given and the results are compared with high-resolution measurements and theoretical calculations.

In stars, ${}^{16}$O represents the endpoint of the helium burning sequence due to the low rate of ${}^{16}$O($\ensuremath{\alpha}$,$\ensuremath{\gamma}$)${}^{20}$Ne. We present a new direct measurement of the total cross section of ${}^{16}$O($\ensuremath{\alpha}$,$\ensuremath{\gamma}$)${}^{20}$Ne at ${E}_{\mathrm{c}.\mathrm{m}.}=1.69\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$ employing the DRAGON recoil separator. In addition, the branching ratios and strength of the ${E}_{\mathrm{c}.\mathrm{m}.}=2.426\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$ ${3}^{\ensuremath{-}}$ resonance were determined.

In a recent experiment performed at Triumf using the Dragon 0° spectrometer and its associated BGO array, the complete γ-decay of the radiative capture channel below the Coulomb barrier has been measured for the first time. This measurement has been performed at two energies Ec.m. = 6.6 and 7.2 MeV. A selective contribution of the entrance spins 2+ and 3− has been evidenced which is consistent with existing results above the barrier.

In stellar helium burning, ${}^{16}$O represents the endpoint of the helium-burning sequence due to the low rate of ${}^{16}$O($\ensuremath{\alpha}$,$\ensuremath{\gamma}$)${}^{20}$Ne. We present a new direct measurement of the total capture reaction rate of ${}^{16}$O($\ensuremath{\alpha}$,$\ensuremath{\gamma}$)${}^{20}$Ne at ${E}_{\mathrm{c}.\mathrm{m}.}=2.26\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$ employing the DRAGON recoil separator. For the first time, the total $S$ factor and its contributing direct capture transitions could be determined in one experiment.

We have performed a heavy ion radiative capture reaction between two light heavy ions, $^{12}$C and $^{16}$O, leading to $^{28}$Si. The present experiment has been performed below Coulomb barrier energies in order to reduce the phase space and to try to shed light on structural effects. Obtained $\gamma$-spectra display a previously unobserved strong feeding of intermediate states around 11 MeV at these energies. This new decay branch is not fully reproduced by statistical nor semi-statistical decay scenarii and may imply structural effects. Radiative capture cross-sections are extracted from the data., Comment: 4 pages, 7 figures, to appear as proceedings of FUSION 2011 conference at St-Malo, France

The {sup 18}F(p,{alpha}){sup 15}O reaction rate is crucial for understanding the final abundance of {sup 18}F predicted by nova models. The {gamma}-ray emission in the first few hours after a nova outburst is expected to be dominated by 511 keV annihilation photons from the decay of {sup 18}F, and so understanding its production can provide important constraints on the conditions during the outburst when compared with observations. Results are presented from the lowest-energy direct measurement to date, performed at the Isotope Separator and Accelerator radioactive beam facility at the TRIUMF laboratory, Canada. Cross section measurements at center-of-mass energies of 250, 330, 453, and 673 keV are obtained and the results compared to previous data and R-matrix calculations. The implications for the overall reaction rate in the context of nova explosions have been discussed.

The lowest-energy resonance in the $^{23}\mathrm{Mg}$($p,\ensuremath{\gamma}$)$^{24}\mathrm{Al}$ reaction, which is dominant at classical nova temperatures, has been measured directly for the first time using the DRAGON recoil spectrometer. The experiment used a radioactive $^{23}\mathrm{Mg}$ beam (mixed within a significantly stronger $^{23}\mathrm{Na}$ beam) of peak intensity $5\ifmmode\times\else\texttimes\fi{}{10}^{7}$ $\mathrm{s}{}^{\ensuremath{-}1}$, at the ISAC facility at TRIUMF. We extract values of ${E}_{R}={485.7}_{\ensuremath{-}1.8}^{+1.3}$ keV and $\ensuremath{\omega}\ensuremath{\gamma}={38}_{\ensuremath{-}15}^{+21}$ meV from our data (all values in the center-of-mass frame unless otherwise stated). In addition, the experiment prompted a recalculation of the $Q$ value for this reaction based on a revision of the $^{24}\mathrm{Al}$ mass. The effect on the uncertainties in the quantities of ejected $^{22}\mathrm{Na}$ and $^{26}\mathrm{Al}$ from oxygen-neon classical novae is discussed.

The ${Q}_{\mathrm{EC}}$ value of the superallowed $\ensuremath{\beta}$ emitter $^{26}\mathrm{Si}$ has been measured with the JYFLTRAP Penning trap facility to be 4840.85(10) keV which is ten times more precise than any previous measurement. This leaves only the branching ratio to be improved before the $\mathcal{F}t$ value of $^{26}\mathrm{Si}$ can be used to test the conserved vector current hypothesis. As a consequence, the $^{25}\mathrm{Al}(p,\ensuremath{\gamma})^{26}\mathrm{Si}$ reaction $Q$-value (${Q}_{p\ensuremath{\gamma}}$) was improved to be 5513.7(5) keV, limited now by the mass excess of $^{25}\mathrm{Al}$. The new ${Q}_{p\ensuremath{\gamma}}$ value changes the stellar production rate of $^{26}\mathrm{Si}$ in nova ignition temperatures by about 10%.

Atomic masses of the neutron-rich isotopes $^{76--80}\mathrm{Zn}$, $^{78--83}\mathrm{Ga}$, $^{80--85}\mathrm{Ge}$, $^{81--87}\mathrm{As}$, and $^{84--89}\mathrm{Se}$ have been measured with high precision using the Penning trap mass spectrometer JYFLTRAP at the IGISOL facility. The masses of $^{82,83}\mathrm{Ga}$, $^{83--85}\mathrm{Ge}$, $^{84--87}\mathrm{As}$, and $^{89}\mathrm{Se}$ were measured for the first time. These new data represent a major improvement in the knowledge of the masses in this neutron-rich region. Two-neutron separation energies provide evidence for the reduction of the $N=50$ shell gap energy towards germanium ($Z=32$) and a subsequent increase at gallium ($Z=31$). The data are compared with a number of theoretical models. An indication of the persistent rigidity of the shell gap towards nickel ($Z=28$) is obtained.

A high-precision direct Penning trap mass measurement has revealed a 0.5-MeV deviation of the binding energy of (134)Sn from the currently accepted value. The corrected mass assignment of this neutron-rich nuclide restores the neutron-shell gap at N=82, previously considered to be a case of "shell quenching." In fact, the new shell gap value for the short-lived (132)Sn is larger than that of the doubly magic (48)Ca which is stable. The N=82 shell gap has considerable impact on fission recycling during the r process. More generally, the new finding has important consequences for microscopic mean-field theories which systematically deviate from the measured binding energies of closed-shell nuclides.

High-precision Penning trap mass measurements on the stable nuclide 27Al as well as on the short-lived radionuclides 26Al and 38,39Ca have been performed by use of radiofrequency excitation with time-separated oscillatory fields, i.e. Ramsey's method, as recently introduced for the excitation of the ion motion in a Penning trap, was applied. A comparison with the conventional method of a single continuous excitation demonstrates its advantage of up to ten times shorter measurements. The new mass values of 26,27Al clarify conflicting data in this specific mass region. In addition, the resulting mass values of the superallowed beta-emitter 38Ca as well as of the groundstate of the beta-emitter 26Al m confirm previous measurements and corresponding theoretical corrections of the ft-values., Comment: 7 pages, 9 figures

Ramsey's method of separated oscillatory fields is applied to the excitation of the cyclotron motion of short-lived ions in a Penning trap to improve the precision of their measured mass values. The theoretical description of the extracted ion-cyclotron-resonance line shape is derived and its correctness demonstrated experimentally by measuring the mass of the short-lived 38Ca nuclide with an uncertainty of 1.1 x 10(-8) using the Penning trap mass spectrometer ISOLTRAP at CERN. The mass of the superallowed beta emitter 38Ca contributes for testing the theoretical corrections of the conserved-vector-current hypothesis of the electroweak interaction. It is shown that the Ramsey method applied to Penning trap mass measurements yields a statistical uncertainty similar to that obtained by the conventional technique but 10 times faster. Thus the technique is a new powerful tool for high-precision mass measurements.

International audience; States in 26Na were populated in the (d, pγ) reaction, induced by bombarding deuterium target nuclei with an intense reaccelerated beam of 25Na ions from the ISAC2 accelerator at TRIUMF. Gamma-rays were recorded in coincidence with protons and used to extract differential cross sections for 21 states up to the neutron decay threshold of 5 MeV. Results for levels below 3 MeV are discussed in detail and compared with shell model calculations and with previous work. The angular distributions of decay gamma-rays were measured for individual states and are compared to theoretically calculated distributions, highlighting some issues for future work.

The manipulation of ion beams by trapping techniques at the IGISOL facility is described. Examples of applications of ion traps in spectroscopic studies and mass spectrometry are given.