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Unbound states in 17C were investigated via one-neutron removal from a 18C beam at an energy of 245 MeV/nucleon on a carbon target. The energy spectrum of 17C, above the single-neutron decay threshold, was reconstructed using invariant mass spectroscopy from the measured momenta of the 16C fragment and neutron, and was found to exhibit resonances at Er=0.52(2), 0.77(2), 1.36(1), 1.91(1), 2.22(3) and 3.20(1) MeV. The resonance at Er=0.77(2) MeV [Ex=1.51(3) MeV] was provisionally assigned as the second 5/2+ state. The two resonances at Er=1.91(1) and 3.20(1) MeV [Ex=2.65(2) and 3.94(2) MeV] were identified, through comparison of the energies, cross sections and momentum distributions with shell-model and eikonal reaction calculations, as p-shell hole states with spin-parities 1/2- and 3/2-, respectively. A detailed comparison was made with the results obtained using a range of shell-model interactions. The YSOX shell-model Hamiltonian, the cross-shell part of which is based on the monopole-based universal interaction, was found to provide a very good description of the present results and those for the neighbouring odd-A carbon isotopes - in particular for the negative parity cross-shell states., Physics Letters B 836 (2023) 137629, published

Detailed γ-ray spectroscopy of the exotic neon isotope 28Ne has been performed for the first time using the one-neutron removal reaction from 29Ne on a liquid hydrogen target at 240 MeV/nucleon. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for 28Ne and the negative-parity states are identified for the first time. The measured partial cross sections and momentum distributions reveal a significant intruder p-wave strength providing evidence of the breakdown of the N=20 and N=28 shell gaps. Only a weak, possible f-wave strength was observed to bound final states. Large-scale shell-model calculations with different effective interactions do not reproduce the large p-wave and small f-wave strength observed experimentally, indicating an ongoing challenge for a complete theoretical description of the transition into the island of inversion along the Ne isotopic chain. Detailed $\gamma$-ray spectroscopy of the exotic neon isotope $^{28}$Ne has been performed for the first time using the one-neutron removal reaction from $^{29}$Ne on a liquid hydrogen target at 240~MeV/nucleon. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for $^{28}$Ne and the negative-parity states are identified for the first time. The measured partial cross sections and momentum distributions reveal a significant intruder $p$-wave strength providing evidence of the breakdown of the $N=20$ and $N=28$ shell gaps. Only a weak, possible $f$-wave strength was observed to bound final states. Large-scale shell-model calculations with different effective interactions do not reproduce the large $p$-wave and small $f$-wave strength observed experimentally, indicating an ongoing challenge for a complete theoretical description of the transition into the island of inversion along the Ne isotopic chain.

The nucleus $^{29}$Ne is situated at the border of the island of inversion. Despite significant efforts, no bound low-lying intruder $f_{7/2}$-state, which would place $^{29}$Ne firmly inside the island of inversion, has yet been observed. Here, the first investigation of unbound states of $^{29}$Ne is reported. The states were populated in $^{30}\mathrm{Ne}(p,pn)$ and $^{30}\mathrm{Na}(p,2p)$ reactions at a beam energy of around $230$ MeV/nucleon, and analyzed in terms of their resonance properties, partial cross sections and momentum distributions. The momentum distributions are compared to calculations using the eikonal, direct reaction model, allowing $\ell$-assignments for the observed states. The lowest-lying resonance at an excitation energy of 1.48(4) MeV shows clear signs of a significant $\ell$=3-component, giving first evidence for $f_{7/2}$ single particle strength in $^{29}$Ne. The excitation energies and strengths of the observed states are compared to shell-model calculations using the sdpf-u-mix interaction, Comment: 12 pages, 14 figures, accepted for publication in Physical Review C

An inelastic $��$-scattering experiment on the unstable $N=Z$, doubly-magic $^{56}$Ni nucleus was performed in inverse kinematics at an incident energy of 50 A.MeV at GANIL. High multiplicity for $��$-particle emission was observed within the limited phase-space of the experimental setup. This observation cannot be explained by means of the statistical-decay model. The ideal classical gas model at $kT$ = 0.4 MeV reproduces fairly well the experimental momentum distribution and the observed multiplicity of $��$ particles corresponds to an excitation energy around 96 MeV. The method of distributed $m��$-decay ensembles is in agreement with the experimental results if we assume that the $��$-gas state in $^{56}$Ni exists at around $113^{+15}_{-17}$ MeV. These results suggest that there may exist an exotic state consisting of many $��$ particles at the excitation energy of $113^{+15}_{-17}$ MeV., Accepted for publication in the European Physical Journal A

A comparative study of the neutron-$��$ Pulse Shape Discrimination (PSD) with seven organic scintillators is performed using an identical setup and digital electronics. The scintillators include plastics (EJ-299-33 and a plastic prototype), single crystals (stilbene and the recent doped $p$-terphenyl) and liquids (BC501A, NE213 and the deuterated liquid BC537). First, the overall PSD performance of the different scintillators is compared and threshold neutron energies for a given discrimination quality are determined. Then, using statistical arguments, two intrinsic contributions to the PSD capability of the scintillating materials are disentangled: the light yield and the specific pulse shapes induced by neutrons and $��$-rays. This separation provides additional insight into the behaviour of organic scintillators and allows a detailed comparison of the discrimination performance of the various materials. On the basis of this analysis, limitations of current organic scintillators and of recently proposed alternative scintillators are discussed., Accepted in Nucl. Instr. and Meth. in Phys. Res. A

The kinematics of two-neutron emission following the $��$-decay of $^{11}$Li was investigated for the first time by detecting the two neutrons in coincidence and by measuring their angle and energy. An array of liquid-scintillator neutron detectors was used to reject cosmic-ray and $��$-ray backgrounds by pulse-shape discrimination. Cross-talk events in which two detectors are fired by a single neutron were rejected using a filter tested on the $��$-1n emitter $^9$Li. A large cross-talk rejection rate is obtained ($> 95 \%$) over most of the energy range of interest. Application to $^{11}$Li data leads to a significant number of events interpreted as $��$-2n decay. A discrete neutron line at $\approx$ 2 MeV indicates sequential two-neutron emission, possibly from the unbound state at 10.6 MeV excitation energy in $^{11}$Be., 4 pages, Proceedings of the EuNPC2018 Conference

The half-life of $^{19}$Ne has been measured using a real-time digital multiparametric acquisition system providing an accurate time-stamp and relevant information on the detectors signals for each decay event. An exhaustive offline analysis of the data gave unique access to experimental effects potentially biasing the measurement. After establishing the influence factors impacting the measurement such as after-pulses, pile-up, gain and base line fluctuations, their effects were accurately estimated and the event selection optimized. The resulting half-life, $17.2569\pm0.0019_{(stat)}\pm0.0009_{(syst)}$~s, is the most precise up to now for $^{19}$Ne. It is found in agreement with two recent precise measurements and not consistent with the most recent one [L.J. Broussard {\it et al.}, Phys. Rev. Lett. {\bf112}, 212301 (2014)] by 3.0 standard deviations. The full potential of the technique for nuclei with half-lives of a few seconds is discussed., Comment: 11 pages, 16 figures

The most intense gamma-ray line observable from novae is likely to be from positron annihilation associated with the decay of 18F. The uncertainty in the destruction rate of this nucleus through the 18F(p,��)15O reaction presents a limit to interpretation of any future observed gamma-ray flux. Direct measurements of the cross section of both this reaction and the 18F(p,p)18F reaction have been performed between center of mass energies of 0.5 and 1.9 MeV. Simultaneous fits to both data sets with the R-Matrix formalism reveal several resonances, with the inferred parameters of populated states in 19Ne in general agreement with previous measurements. Of particular interest, extra strength has been observed above ECM \sim1.3 MeV in the 18F(p,p)18F reaction and between 1.3-1.7 MeV in the 18F(p,��)15O reaction. This is well described by a broad 1/2+ state, consistent with both a recent theoretical prediction and an inelastic scattering measurement. The astrophysical implications of a broad sub-threshold partner to this state are discussed., 7 pages, 4 figures, 2 tables

The structure of $^{44}$S has been studied using delayed $\gamma$ and electron spectroscopy at \textsc{ganil}. The decay rates of the 0$^+_2$ isomeric state to the 2$^+_1$ and 0$^+_1$ states have been measured for the first time, leading to a reduced transition probability B(E2~:~2$^{+}_1$$\rightarrow$0$^{+}_2)$= 8.4(26)~e$^2$fm$^4$ and a monopole strength $\rho^2$(E0~:~0$^{+}_2$$\rightarrow$0$^{+}_1)$ =~8.7(7)$\times$10$^{-3}$. Comparisons to shell model calculations point towards prolate-spherical shape coexistence and a phenomenological two level mixing model is used to extract a weak mixing between the two configurations., Comment: 5 pages, 3 figures, accepted for publication in Physical Review Letters

A new and independent determination of the Gamow-Teller branching ratio in the beta-decay of 21Na is reported. The value obtained of 5.13 +- 0.43 % is in agreement with the currently adopted value and the most recent measurement. In contrast to previous experiments, the present method was based on the counting of the parent 21Na ions and the resulting 351 keV gamma-rays without coincident beta-particle detection., 12 pages, 10 figures Published online in Journal of Physics G: Nuclear and Particle Physics

In an experiment performed at the LISE3 facility of GANIL, we studied the decay of 22Al produced by the fragmentation of a 36Ar primary beam. A beta-decay half-life of 91.1 +- 0.5 ms was measured. The beta-delayed one- and two-proton emission as well as beta-alpha and beta-delayed gamma decays were measured and allowed us to establish a partial decay scheme for this nucleus. New levels were determined in the daughter nucleus 22Mg. The comparison with model calculations strongly favours a spin-parity of 4+ for the ground state of 22Al.