The investigation of the effects of average atomic ionization on nuclear reactions is of prime importance for nuclear astrophysics. No direct experimental measurement using a plasma target has been done yet. In this regard, we measured for the first time the neutron production of a (p,n) reaction in different states of ionization. The studied nuclear reaction was 51V(p,n)51Cr. We measured a significantly lower neutron production than expected when the target was ionized, even when taking into account existing electron screening theory or the effect of the stopping power in the target on the injected proton beam. This experiment is a first step in the process to characterize the influence of ionization at astrophysically relevant energies.

Here we report on the measurements of the gamma -ray strength functions and nuclear level densities of 112,114Sn performed for the first time at the 9-MV Tandem accelerator facilities at Horia Hulubei Institute for Physics and Nuclear Engineering using the Oslo method. We extract thermodynamic properties and gross and fine properties of the pygmy dipole resonance for systematic comparison in the chain of Sn isotopes. The results are compared with microscopic models implemented in the TALYS reaction code and the fully microscopic quasiparticlephonon model for the underlying nuclear structure of the dipole strength in 112,114Sn. The quasiparticle-phonon model results show the importance of complex configurations to the low-energy dipole response in the pygmy dipole resonance energy region. The experimental data are further included in the cross section and reaction rate calculations for the (n, gamma ) reaction of the p-process nuclei 112,114Sn showing a significant increase in reaction rates at high temperatures compared to existing nuclear databases.

Background: The nuclear structure of low-lying excited states in I-139, a neutron-rich nucleus with Z = 53 and N = 86 above Sn-132 and in the proximity of A similar to 140, is investigated. Purpose: The decay scheme for I-139 is obtained after the first beta-decay measurement of Te-139. Transitions in I-138 are detected after the beta-delayed neutron emission of Te-139. The Pn ratio is investigated based on the gamma-ray emissions. Methods: beta-delayed. -ray spectroscopy is employed to study excited states in I-139, populated in the decay of a mass-separated beam of Te-139, produced in the in-flight fission of U-235 on a Be-9 target. Results: The new level scheme of I-139 with 26 new transitions, established for the first time in beta decay, is reported. Two new transitions are observed also in I-138. The beta-delayed neutron emission probability P-n of Te-139 is deduced to be 17.6(48)%. New and/or more restrictive spin/parity assignments of states in the daughter I-138 nucleus are reported as well. Conclusions: The experimental results are an important input to the theoretical description of nuclei in the region, being well interpreted within large-scale shell-model calculations, and provide essential information on the first-forbidden transitions beyond N = 82 and Z = 50.

The known I^{π}=8_{1}^{+}, E_{x}=2129-keV isomer in the semimagic nucleus ^{130}Cd_{82} was populated in the projectile fission of a ^{238}U beam at the Radioactive Isotope Beam Factory at RIKEN. The high counting statistics of the accumulated data allowed us to determine the excitation energy, E_{x}=2001.2(7)  keV, and half-life, T_{1/2}=57(3)  ns, of the I^{π}=6_{1}^{+} state based on γγ coincidence information. Furthermore, the half-life of the 8_{1}^{+} state, T_{1/2}=224(4)  ns, was remeasured with high precision. The new experimental information, combined with available data for ^{134}Sn and large-scale shell model calculations, allowed us to extract proton and neutron effective charges for ^{132}Sn, a doubly magic nucleus far-off stability. A comparison to analogous information for ^{100}Sn provides first reliable information regarding the isospin dependence of the isoscalar and isovector effective charges in heavy nuclei.

. - The high-energy gamma-rays from the GDR decay of 56,60,62Ni* nuclei at finite temperature, produced in the reactions 32,34,36S + 24,26Mg at bombarding energies between 78 , 90 MeV, were measured and analyzed with statistical model using a Monte Carlo approach. It is found that the present analysis gives some evidence on the presence of an extra yield on the tail of the Giant Dipole Resonance which may be attributed to a Pygmy Dipole Resonance in an excited nucleus.

Background: The nuclear structure of low-lying excited states in 139 I, a neutron-rich nucleus with Z = 53 and N = 86 above 132 Sn and in the proximity of A similar to 140, is investigated. Purpose: The decay scheme for 139I is obtained after the first /3-decay measurement of 139 Te. Transitions in 138I are detected after the /3-delayed neutron emission of 139 Te. The Pn ratio is investigated based on the gamma-ray emissions. Methods: /3-delayed gamma-ray spectroscopy is employed to study excited states in 139 I, populated in the decay of a mass-separated beam of 139 Te, produced in the in-flight fission of 235U on a 9 Be target. Results: The new level scheme of 139I with 26 new transitions, established for the first time in /3 decay, is reported. Two new transitions are observed also in 138 I. The /3-delayed neutron emission probability Pn of 139 Te is deduced to be 17.6(48)%. New and/or more restrictive spin/parity assignments of states in the daughter 138I nucleus are reported as well. Conclusions: The experimental results are an important input to the theoretical description of nuclei in the region, being well interpreted within large-scale shell-model calculations, and provide essential information on the first-forbidden transitions beyond N = 82 and Z = 50.

Since two decades, laser-driven neutron emissions are studied as they represent a complementary source to conventional neutron sources, with further more different characteristics (i.e. shorter bunch duration and higher number of neutrons per bunch). We report here a global, thorough characterization of the neutron fields produced at the Apollon laser facility using the secondary laser beam (F2). A Double Plasma Mirror (DPM) was used to improve the temporal contrast of the laser which delivers pulses of 24 fs duration, a mean on-target energy of ~10 J and up to 1 shot/min. The interaction of the laser with thin targets (few tens or hundreds of nm) in ultra-high conditions produced enhanced proton beams (up to 35 MeV), which were then used to generate neutrons via the pitcher-catcher technique. The characterization of these neutron emissions is presented, with results obtained from both simulations and measurements using several diagnostics (activation samples, bubble detectors and Time-of-Flight detectors), leading to a neutron yield of ~$4.10^{7}$ neutrons/shot. Similar neutron emissions were observed during shots with and without DPM, while fewer X-rays are produced when the DPM is used, making this tool interesting to adjust the neutrons/X-rays ratio for some applications like combined neutron/X-ray radiography.

We have performed the measurement of the 27Al(α, n) cross section at IFIN-HH for a range of energies from 2.5 to 5.2 MeV, using an array of 28 3He counters arranged in 3 concentric rings (ELIGANT-TN). Here we present the experimental setup and discuss the role of the 13C contamination which effects the measurements in the low-energy region. Energy-dispersive X-ray spectroscopy carried out before and after the experiment suggested an increase in the 13C concentration during the experiment.

. - The ELIGANT set of instruments is a dedicated tool being developed at ELI-NP for studying high-energy collective nuclear excitations using gamma beams. The topics of interest in these studies range from fundamental nuclear structure properties of the Giant Dipole Resonance and the low-energy strength enhancement in the Pygmy Dipole Resonance region, to applications in p-process nucleosynthesis and propagation of Ultra-High Energy Cosmic Rays. The equipment consists of large-volume LaBr3:Ce and CeBr3 detectors for high-energy gamma-rays, liquid scintillators and lithium glass scintillators for high-and low-energy neutron time-of-flight, and a proportional counter system of 3He tubes for cross-section measurements. These instruments have been installed and commissioned with sources and via in beam measurements, in different configurations, at the IFIN-HH Tandem/Tandetron accelerators with terminal voltages of 3 MV and 9 MV. This contribution gives an overview of the present and future activities with ELIGANT.

We performed an experiment to measure weak-y-decay branching ratios and study angular distributions of-y-decay transitions in 10B for constraining ab initio calculations at the 9 MV Tandem accelerator of the Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH). In the experi-ment, large-volume LaBr3:Ce and CeBr3 scintillators having sufficient efficiency for high energy-y rays were used. In this paper, we present-y-ray intensities obtained from single-y-decay spectra emitted in the 10B(p, p/-y)10B* reaction at 8.5 MeV.

Excited states in B10 were populated with the B10(p,p′γ)B10* reaction at 8.5 MeV and their γ decay was investigated via coincidence γ-ray spectroscopy. The emitted γ rays were measured using large-volume LaBr3:Ce and CeBr3 detectors placed in anti-Compton shields. This allowed the observation of weak γ-ray transitions, such as the M3 transition between the Jπ,T=0+,1 isobaric analog state (IAS) and the Jπ,T=3+,0 ground state and the E2 transition between the Jπ,T=21+,0 state and the IAS, i.e., performing measurements of branching ratios at the level of λ≥10−4. For the first time in B10, the competing M1 and M3 transitions from the decay of the IAS have been observed in a γ spectroscopy experiment. The experimental results are compared with ab initio no-core shell model calculation using the newest version of the local position-space chiral N3LO nucleon-nucleon interaction. The calculations reproduce correctly the ordering of the bound states in B10, and are in reasonable agreement with the observed branching ratios and reduced transition probabilities.Received 29 February 2024Revised 14 May 2024Accepted 21 June 2024DOI:https://doi.org/10.1103/PhysRevLett.133.072502© 2024 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasElectromagnetic transitionsInelastic scattering reactionsNuclear many-body theoryNuclear structure & decaysNucleon-nucleon interactionsProperties6 ≤ A ≤ 19Nuclear Physics

Photonuclear reactions of light nuclei below a mass of A=60 are planned to be studied experimentally and theoretically with the PANDORA (Photo-Absorption of Nuclei and Decay Observation for Reactions in Astrophysics) project. Two experimental methods, virtual photon excitation by proton scattering and real photo absorption by a high-brilliance γ -ray beam produced by laser Compton scattering, will be applied to measure the photoabsorption cross sections and decay branching ratio of each decay channel as a function of the photon energy. Several nuclear models, e.g. anti-symmetrized molecular dynamics, mean-field and beyond-mean-field models, a large-scale shell model, and ab initio models, will be employed to predict the photonuclear reactions. The uncertainty in the model predictions will be evaluated based on the discrepancies between the model predictions and experimental data. The data and predictions will be implemented in the general reaction calculation code, TALYS. The results will be applied to the simulation of the photo-disintegration process of ultra-high-energy cosmic rays in inter-galactic propagation.

We have performed the first experimental campaign using large-volume LaBr3:Ce and CeBr3 detectors from several of the Extreme Light Infrastructure-Nuclear physics (ELI-NP) instrumental setups together with detectors and infrastructure from the ROSPHERE array at the 9 MV Tandem facility at the Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH). The performance of the detectors and the digital data acquisition system is shown to give a good energy resolution at high energies, and an excellent time resolution. We, furthermore, present the possibilities to integrate the detector system and the digital electronics with various ancillary detectors for, for example, charged particles.

The ^19 F(p, α ) ^16 O reaction is of paramount importance for understanding the fluorine abundance in the outer layers of asymptotic giant branch (AGB) stars and it might also play a role in hydrogen-deficient post-AGB star nucleosynthesis. Theoretical models overestimate F abundances in AGB stars with respect to the observed values, thus calling for further investigation of the reactions involved in the fluorine nucleosynthesis. In the last years, new direct and indirect measurements improved significantly the knowledge of the ^19 F(p, α _0 ) ^16 O cross section at deeply sub-Coulomb energies (below 0.8 MeV). Those data are larger by a factor of about 1.4 with respect to the previous data reported in the NACRE compilation in the energy region 0.6–0.8 MeV. In order to solve these discrepancies, here we present a new direct experiment performed using a silicon strip detector array (LHASA – Large High-resolution Array of Silicon for Astrophysics). Our results clearly confirm the trend of the latest experimental data in the energy region of interest, pointing towards a larger S-factor value than the one reported in the NACRE compilation.

We have designed and constructed a high-energy gamma-ray source for detector characterisation and calibration. The source is a composite type based on a plutonium-beryllium neutron emitter embedded in a paraffin moderator, which is homogeneously mixed with nickel powder. The 9 MeV gamma-ray source produces approximately 450 photons per second in 4 pi when 2.2 x 10(5) neutrons per second are emitted, corresponding to a surface flux of 9 MeV gamma-rays of approximately 2.5 x 10(-6) cm(-2) per emitted neutron. Here we discuss the properties and design of this source, including the characterisation of homogeneity and high-energy y-ray emission spectra.

Nuclei in the vicinity of 78Ni are important benchmarks for nuclear structure, which can reveal changes in the shell structure far from stability. Spectroscopy of the odd-odd isotope 78Cu was performed for the first time in an experiment with the EURICA setup at the Radioactive Isotope Beam Factory at RIKEN Nishina Center. Excited states in the neutron-rich isotope were populated following the beta decay of 78Ni produced by in-flight fission and

Isomeric states were observed in nuclei produced in an experiment at the RIKEN Nishina Center Radioactive Isotope Beam Factory following the in-flight fission of a 345 MeV/nucleon ^238 U beam. Isomers reported in nuclei spanning a predicted prolate-oblate shape change boundary, ^111 Zr ( E=283.1 keV; τ =0.326(63) s), ^112 Nb ( E=44.2 keV; τ =0.094(26) s), ^113 Nb ( E=135.4 keV; τ =0.846(80) s), and ^115 Mo ( E=198.6 keV; τ =63(4) s), are compared to potential-energy surface calculations which gave a selection of low-lying configurations for each nucleus. Tentative assignments of ground and excited states were made based on energy similarities to the calculations, reduced transition probabilities of the decays, and constraints of transition multipolarities from γ -ray coincidence measurements. These assignments are suggestive of significant deformation being persistent for N>70 in this region. In addition, isomers in ^108 Nb, ^109 Nb, ^113 Tc, ^117 Ru, ^119 Ru, ^120 Rh, and ^122 Rh, not spanning the prolate-oblate transition discussed, are presented.