In the interest of exploring resonant contributions to the radiative capture reaction ^45 V(p, γ ) ^46 Cr, which is identified to impact the ^44 Ti nucleosynthesis in Core Collapse Supernovae at astrophysical energies, we performed a spectroscopic study of ^46 Cr through the β -decay of the progenitor ^46 Mn. We present new results on the decay scheme of the proton-rich exotic nucleus ^46 Mn based on a new approach at the level of the experimental data analysis. ^46 Mn was produced among other nuclei at the LISE3 fragment separator operated in GANIL using the fragmentation technique. The novel approach is compared with a traditional data analysis, and validated using the known decay scheme of ^45 Cr. The observed level scheme of the nucleus ^46 Cr is compared with previous works. This work confirms former experimental results, while presenting better statistics and revealing new transitions in the decay scheme.

We report an uncertainty-controlled determination of neutron-removal spectroscopic factors in the neutron-deficient p-shell nuclei ^12C, ^10C, ^9C, and ^8B, all measured under uniform conditions through exclusive ground-state-to-ground-state (p,d) reactions at about 50 MeV/nucleon in a liquid hydrogen target at the GANIL/LISE facility. The deuterons were detected in the highly-segmented MUST2 detector placed at forward angles and the excitation energy was reconstructed by the missing mass method. Several transitions, including a new state in ^7B, were observed. Differential cross sections, which display an L=1 pattern for all nuclei, were fitted with 416 sets of uncertainty-quantified optical-model potential parameters and considering various single-particle bound-state wavefunctions to derive C^2S values. The ratio between experimental and shell-model calculated values, R_S, is found to be slightly decreasing as a function of increasing proton to neutron separation energy asymmetry ΔS, with a slope of -0.0049(36)_ stat(13)_ omp(8)_ s.p.. The observed trend is compatible with the phenomenological expectation that the short-range correlation effect on C^2S increases with the degree of nucleon minority. The present data set delivers a high-precision benchmark that will tightly constrain future microscopic descriptions of short-range correlations in asymmetric nuclei.

Nuclear astrophysics recently celebrated its 100th anniversary and remains an active field of science. This article reviews several contemporary experimental techniques used to determine nuclear-reaction rates. Additionally, it presents some theoretical aspects directly related to these experimental techniques, providing an introduction to the fundamental principles underlying them. The 18F(p,α)15O reaction, which is associated with γ-ray emission from classical novae during the first hours after expansion, is used as a central theme throughout the article. Several examples of recent experiments are highlighted, particularly those conducted in nuclear facilities utilizing radioactive beams.

Observed abundances of Z ∼ 40 elements in metal-poor stars vary from star to star, indicating that the rapid and slow neutron capture processes may not contribute alone to the synthesis of elements beyond iron. The weak r -process was proposed to produce Z ∼ 40 elements in a subset of old stars. Thought to occur in the ν -driven ejecta of a core-collapse supernova, ( α , xn ) reactions would drive the nuclear flow toward heavier masses at T = 2−5 GK. However, current comparisons between modeled and observed yields do not bring satisfactory insights into the stellar environment, mainly due to the uncertainties of the nuclear physics inputs where the dispersion in a given reaction rate often exceeds 1 order of magnitude. Involved rates are calculated with the statistical model where the choice of an α -optical-model potential ( α OMP) leads to such a poor precision. The first experiment on ^87 Rb( α , xn ) reactions at weak r -process energies is reported here. Total inclusive cross sections were assessed at E _c.m. = 8.1−13 MeV (3.7−7.6 GK) with the active target MUlti-Sampling Ionization Chamber. With an N = 50 seed nucleus, the measured values agree with statistical model estimates using the α OMP Atomki-V2 . A reevaluated reaction rate was incorporated into new nucleosynthesis calculations, focusing on ν -driven ejecta conditions known to be sensitive to this specific rate. These conditions were found to fail to reproduce the lighter heavy element abundances in metal-poor stars.

The MORA experimental setup is designed to measure the triple-correlation D parameter in nuclear beta decay. The D coefficient is sensitive to possible violations of time-reversal invariance. The experimental configuration consists of a transparent Paul trap surrounded by a detection setup with alternating beta and recoil-ion detectors. The octagonal symmetry of the detection setup optimizes the sensitivity of positron-recoil-ion coincidence rates to the D correlation, while reducing systematic effects. MORA utilizes an innovative in-trap laser polarization technique. The design and performance of the ion trap, associated beamline elements, lasers and beta and recoil-ion detectors, are presented. Recent progress towards the polarization proof-of-principle is described.

The main observables of the rare two-proton emission process - half-life, total energy of the decay as well as energy and angular correlations between the emitted protons - have been measured for 48Ni and 45Fe in a recent experiment performed at the GANIL/LISE3 facility. The results, together with previous experimental work, are compared for the first time with calculations performed in the recently developed Gamow Coupled-Channel (GCC) framework and to 3-body predictions from literature. The comparison of the 48Ni and the 45Fe two-proton angular distributions with the GCC calculations confirms the adopted strength of the proton-proton interaction for both nuclei and the predominant small-angle emission. A comparison with 3-body model angular distributions indicates the shell closure of the f_7/2 orbital for 48Ni and a substantial occupancy of the p-orbital for 45Fe. Discrepancies between experimental data and theoretical predictions are found when studying the other observables: half-lives, total energy of the decay and energy correlations, showing the complexity of the description of the two-proton emission process.

The efficiency of the weak s process in low-metallicity rotating massive stars depends strongly on the rates of the competing ^{17}O(α,n)^{20}Ne and ^{17}O(α,γ)^{21}Ne reactions that determine the potency of the ^{16}O neutron poison. Their reaction rates are poorly known in the astrophysical energy range of interest for core helium burning in massive stars because of the lack of spectroscopic information (partial widths, spin parities) for the relevant states in the compound nucleus ^{21}Ne. In this Letter, we report on the first experimental determination of the α-particle spectroscopic factors and partial widths of these states using the ^{17}O(^{7}Li,t)^{21}Ne α-transfer reaction. With these the ^{17}O(α,n)^{20}Ne and ^{17}O(α,γ)^{21}Ne reaction rates were evaluated with uncertainties reduced by a factor more than 3 with respect to previous evaluations and the present ^{17}O(α,n)^{20}Ne reaction rate is more than 20 times larger. The present (α,n)/(α,γ) rate ratio favors neutron recycling and suggests an enhancement of the weak s process in the Zr-Nd region by more than 1.5 dex in metal-poor rotating massive stars.

Missing mass spectroscopy of the unbound C-8 nucleus was performed by the one-neutron transfer 9C(p,d)8C reaction at 55 MeV/nucleon. Besides the known ground state, two new resonant states were observed, the first at an excitation energy of 3.40(25) MeV with a width of 3.0(5) MeV, the second at 18.6(5) MeV with a width of 3.9(11) MeV. Spin and parity J(pi)=2(+) were assigned to the first resonance from the distorted-wave Born approximation analysis of the experimental differential cross section. The excitation energy of the 2(+) resonance in C-8 supports the persistence of the subshell closure at the semimagic number Z = 6, as is the case for N = 6. The mirror energy difference relative to the 2(+ )state in 8He, Delta E-x=-0.14(25) MeV, is compatible with zero. Both states represent resonances in the continuum, unbound by about 1.4 and 6.9 MeV, respectively, above the particle thresholds. A simple theoretical model emphasizes the difference in unboundedness to account for a symmetry in mirror energies. This unique system is expected to provide a salient test of theoretical models, which include the treatment of the continuum.

Missing mass spectroscopy of the unbound $^{8}\mathrm{C}$ nucleus was performed by the one-neutron transfer $^{9}\mathrm{C}(p,d)^{8}\mathrm{C}$ reaction at 55 MeV/nucleon. Besides the known ground state, two new resonant states were observed, the first at an excitation energy of 3.40(25) MeV with a width of 3.0(5) MeV, the second at 18.6(5) MeV with a width of 3.9(11) MeV. Spin and parity ${J}^{\ensuremath{\pi}}={2}^{+}$ were assigned to the first resonance from the distorted-wave Born approximation analysis of the experimental differential cross section. The excitation energy of the ${2}^{+}$ resonance in $^{8}\mathrm{C}$ supports the persistence of the subshell closure at the semimagic number $Z$ = 6, as is the case for $N$ = 6. The mirror energy difference relative to the ${2}^{+}$ state in $^{8}\mathrm{He}, \mathrm{\ensuremath{\Delta}}{E}_{\mathrm{x}}=\ensuremath{-}0.14$(25) MeV, is compatible with zero. Both states represent resonances in the continuum, unbound by about 1.4 and 6.9 MeV, respectively, above the particle thresholds. A simple theoretical model emphasizes the difference in unboundedness to account for a symmetry in mirror energies. This unique system is expected to provide a salient test of theoretical models, which include the treatment of the continuum.

The efficiency of the weak $s$ process in low-metallicity rotating massive stars depends strongly on the rates of the competing $^{17}\mathrm{O}(\ensuremath{\alpha},n)^{20}\mathrm{Ne}$ and $^{17}\mathrm{O}(\ensuremath{\alpha},\ensuremath{\gamma})^{21}\mathrm{Ne}$ reactions that determine the potency of the $^{16}\mathrm{O}$ neutron poison. Their reaction rates are poorly known in the astrophysical energy range of interest for core helium burning in massive stars because of the lack of spectroscopic information (partial widths, spin parities) for the relevant states in the compound nucleus $^{21}\mathrm{Ne}$. In this Letter, we report on the first experimental determination of the $\ensuremath{\alpha}$-particle spectroscopic factors and partial widths of these states using the $^{17}\mathrm{O}(^{7}\mathrm{Li},t)^{21}\mathrm{Ne}$ $\ensuremath{\alpha}$-transfer reaction. With these the $^{17}\mathrm{O}(\ensuremath{\alpha},n)^{20}\mathrm{Ne}$ and $^{17}\mathrm{O}(\ensuremath{\alpha},\ensuremath{\gamma})^{21}\mathrm{Ne}$ reaction rates were evaluated with uncertainties reduced by a factor more than 3 with respect to previous evaluations and the present $^{17}\mathrm{O}(\ensuremath{\alpha},n)^{20}\mathrm{Ne}$ reaction rate is more than 20 times larger. The present $(\ensuremath{\alpha},n)/(\ensuremath{\alpha},\ensuremath{\gamma})$ rate ratio favors neutron recycling and suggests an enhancement of the weak $s$ process in the Zr-Nd region by more than 1.5 dex in metal-poor rotating massive stars.

Background: Globular clusters show strong correlations between different elements, such as the well-known sodium-oxygen anticorrelation. One of the main sources of uncertainty in this anticorrelation is the $^{22}$Ne($p,\gamma$)$^{23}$Na reaction rate, due to the possible influence of an unobserved resonance state at $E_\mathrm{x} = 8862$ keV ($E_\mathrm{r, c.m.} = 68$ keV). The influence of two higher-lying resonance states at $E_\mathrm{x} = 8894$ and $9000$ keV has already been ruled out by direct $^{22}$Ne($p,\gamma$)$^{23}$Na measurementsPurpose: To study excited states in $^{23}$Na above the proton threshold to determine if the unconfirmed resonance states in $^{23}$Na exist. Methods: The non-selective proton inelastic scattering reaction at low energies was used to search for excited states in $^{23}$Na above the proton threshold. Protons scattered from various targets were momentum-analysed in the Q3D magnetic spectrograph at the Maier-Leibnitz Laboratorium, Munich, Germany. Results: The resonance states previously reported at $E_\mathrm{x} = 8862$, $8894$ and $9000$ keV in other experiments were not observed in the present experiment at any angle. This result, combined with other non-observations of these resonance states in most other experiments, results in a strong presumption against the existence of these resonance states. Conclusions: The previously reported resonance states at $E_\mathrm{x} = 8862$, $8894$ and $9000$ keV are unlikely to exist and should be omitted from future evaluations of the $^{22}$Ne($p,\gamma$)$^{23}$Na reaction rates. Indirect studies using low-energy proton inelastic scattering are a simple and yet exceptionally powerful tool in helping to constrain astrophysical reaction rates by providing non-selective information of the excited states of nuclei.

Background: Globular clusters show strong correlations between different elements, such as the well-known sodium-oxygen anticorrelation. One of the main sources of uncertainty in this anticorrelation is the $^{22}\mathrm{Ne}(p,\ensuremath{\gamma})^{23}\mathrm{Na}$ reaction rate, due to the possible influence of an unobserved resonance state at ${E}_{x}=8862$ keV (${E}_{\mathrm{r},\mathrm{c}.\mathrm{m}.}=68$ keV). The influence of two higher-lying resonance states at ${E}_{x}=8894$ and 9000 keV has already been ruled out by direct $^{22}\mathrm{Ne}(p,\ensuremath{\gamma})^{23}\mathrm{Na}$ measurements.Purpose: The purpose of this paper is to study excited states in $^{23}\mathrm{Na}$ above the proton threshold to determine if the unconfirmed resonance states in $^{23}\mathrm{Na}$ exist.Methods: The nonselective proton inelastic-scattering reaction at low energies was used to search for excited states in $^{23}\mathrm{Na}$ above the proton threshold. Protons scattered from various targets were momentum-analyzed in the Q3D magnetic spectrograph at the Maier-Leibnitz Laboratorium, Munich, Germany.Results: The resonance states previously reported at ${E}_{x}=8862$, 8894, and 9000 keV in other experiments were not observed in the present experiment at any angle. This result, combined with other nonobservations of these resonance states in most other experiments, results in a strong presumption against the existence of these resonance states.Conclusions: The previously reported resonance states at ${E}_{x}=8862$, 8894, and 9000 keV are unlikely to exist and should be omitted from future evaluations of the $^{22}\mathrm{Ne}(p,\ensuremath{\gamma})^{23}\mathrm{Na}$ reaction rates. Indirect studies using low-energy proton inelastic scattering are a simple and yet exceptionally powerful tool in helping to constrain astrophysical reaction rates by providing nonselective information of the excited states of nuclei.

Background: Globular clusters show strong correlations between different elements, such as the well-known sodium-oxygen anticorrelation. One of the main sources of uncertainty in this anticorrelation is the 22Ne(p, gamma) 23Na reaction rate, due to the possible influence of an unobserved resonance state at Ex = 8862 keV (Er,c.m. = 68 keV). The influence of two higher-lying resonance states at Ex = 8894 and 9000 keV has already been ruled out by direct 22Ne(p, gamma) 23Na measurements.Purpose: The purpose of this paper is to study excited states in 23Na above the proton threshold to determine if the unconfirmed resonance states in 23Na exist.Methods: The nonselective proton inelastic-scattering reaction at low energies was used to search for excited states in 23Na above the proton threshold. Protons scattered from various targets were momentum-analyzed in the Q3D magnetic spectrograph at the Maier-Leibnitz Laboratorium, Munich, Germany.Results: The resonance states previously reported at Ex = 8862, 8894, and 9000 keV in other experiments were not observed in the present experiment at any angle. This result, combined with other nonobservations of these resonance states in most other experiments, results in a strong presumption against the existence of these resonance states.Conclusions: The previously reported resonance states at Ex = 8862, 8894, and 9000 keV are unlikely to exist and should be omitted from future evaluations of the 22Ne(p, gamma) 23Na reaction rates. Indirect studies using low-energy proton inelastic scattering are a simple and yet exceptionally powerful tool in helping to constrain astrophysical reaction rates by providing nonselective information of the excited states of nuclei.

The last proton bound calcium isotope 35Ca has been studied for the first time, using the 37Ca(p; t)35Ca two neutron transfer reaction. The radioactive 37Ca nuclei, produced by the LISE spectrometer at GANIL, interacted with the protons of the liquid hydrogen target CRYPTA, to produce tritons t that were detected in the MUST2 detector array, in coincidence with the heavy residues Ca or Ar. The atomic mass of 35Ca and the energy of its first 3/2+ state are reported. A large N = 16 gap of 4.61(11) MeV is deduced from the mass measurement, which together with other measured properties, makes 36Ca a doubly magic nucleus. The N = 16 shell gaps in 36Ca and 24O are of similar amplitude, at both edges of the valley of stability. This feature is discussed in terms of nuclear forces involved, within state-of-the-art shell model calculations. Even though the global agreement with data is quite convincing, the calculations underestimate the size of the N = 16 gap in 36Ca by 840 keV.

Classical novae are thermonuclear explosions in stellar binary systems, and important sources of 26 Al and 22 Na. While γ rays from the decay of the former radioisotope have been observed throughout the Galaxy, 22 Na remains untraceable. Its half-life (2.6 yr) would allow the observation of its 1.275 MeV γ -ray line from a cosmic source. However, the prediction of such an observation requires good knowledge of its nucleosynthesis. The 22 Na( p , γ ) 23 Mg reaction remains the only source of large uncertainty about the amount of 22 Na ejected. Its rate is dominated by a single resonance on the short-lived state at 7785.0(7) keV in 23 Mg. Here, we propose a combined analysis of particle-particle correlations and velocity-difference profiles to measure femtosecond nuclear lifetimes. The application of this method to the study of the 23 Mg states, places strong limits on the amount of 22 Na produced in novae and constrains its detectability with future space-borne observatories.

In this work we present the preliminary results of analysing the 46 Mn β + decay channel as a way to study the 45 V( p , γ ) 46 Cr reaction. 46 Mn was selected among other species in the cocktail beam delivered by the LISE fragment separator at GANIL (Caen, France) in order to study its beta decay and the excited states of its daughter nucleus 46 Cr. As part of the validation process we present the 46 Mn half-life, the proton and gamma emission peaks related to the 46 Mn decay and compare them with the results from previous works.

Subjecting a physical system to extreme conditions is one of the means often used to obtain a better understanding and deeper insight into its organization and structure. In the case of the atomic nucleus, one such approach is to investigate isotopes that have very different neutron-to-proton ( N / Z ) ratios than in stable nuclei. Light, neutron-rich isotopes exhibit the most asymmetric N / Z ratios and those lying beyond the limits of binding, which undergo spontaneous neutron emission and exist only as very short-lived resonances (about 10 −21 s), provide the most stringent tests of modern nuclear-structure theories. Here we report on the first observation of 28 O and 27 O through their decay into 24 O and four and three neutrons, respectively. The 28 O nucleus is of particular interest as, with the Z = 8 and N = 20 magic numbers 1 , 2 , it is expected in the standard shell-model picture of nuclear structure to be one of a relatively small number of so-called ‘doubly magic’ nuclei. Both 27 O and 28 O were found to exist as narrow, low-lying resonances and their decay energies are compared here to the results of sophisticated theoretical modelling, including a large-scale shell-model calculation and a newly developed statistical approach. In both cases, the underlying nuclear interactions were derived from effective field theories of quantum chromodynamics. Finally, it is shown that the cross-section for the production of 28 O from a 29 F beam is consistent with it not exhibiting a closed N = 20 shell structure.

Simulations of explosive nucleosynthesis in novae predict the production of 22Na, a key astronomical observable to constrain nova models. Its gamma-ray line at 1.275 MeV has not yet been observed by the gamma-ray space telescopes. The 20Ne/22Ne ratio in presolar grains, a possible tool to identify nova grains, also depends on 22Na produced. Uncertainties on its yield in classical novae currently originate from the rate of the 22Na(p, γ)23Mg reaction. At peak novae temperatures, this reaction is dominated by a resonance at ER=0.204 MeV, corresponding to the Ex=7.785 MeV excited state in 23Mg. The resonance strengths measured so far disagree by one order of magnitude. An experiment has been performed at GANIL to measure the lifetime and the proton branching ratio of this key state, with a femtosecond resolution for the former. The reactions populating states in 23Mg have been studied with a high resolution detection set-up, i.e. the particle VAMOS, SPIDER and gamma tracking AGATA spectrometers, allowing the measurements of lifetimes and proton branchings. We present here a comparison between experimental results and shell-model calculations, that allowed us to assign the spin and parity of the key state. Rather small values obtained for reduced M1 matrix elements, M(M1) ≲ 0.5 µN, and proton spectroscopic factors, C2Sp<10−2, seem to be beyond the accuracy of the shell model. With the reevaluated 22Na(p, γ)23Mg rate, the 22Na detectability limit and its observation frequency from novae are found promising for the future space telescopes.