We have extracted the nuclear level density of Te-128 from a (p,p 'gamma) scattering experiment using the large-volume LaBr3:Ce and CeBr3 detectors from ELI-NP at the 9 MV Tandem facilities at IFIN-HH. The decay data were normalised using photonuclear data, resulting in nuclear level densities without intrinsic model dependencies from the constant temperature or Fermi gas models. The deduced nuclear level density follows in between the expectations from these two models, but we observe a clear divergence from a microscopic model based on the Skyrme force.

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.

In the period 2022-2025, four experimental campaigns were car­ried out at the 9 MW tandem accelerator of IFIN-HH using the large-volume LaBr3 :Ce and CeBr3 detectors of the ELIGANT-GN array, which were placed in the anti-Compton shields of the ROSPHERE. As a result, a highly efficient spec­trometer, ELIFANT, was assembled for the detection of high-energy gamma rays. In the experiments, nuclear level densities and γ-strength functions were studied, as well as weak γ-ray transitions in light nuclei. In the paper, the per­formance of the spectrometer is described, the goals of the campaigns are sum­marized, and first results are presented, e.g., the γ-ray spectroscopy in 10B and the γ-strength functions in 112,114Sn. The ELIGANT-GN array was also used to study neutron and γ-ray angular and energy correlations in spontaneous fission of 252Cf. First results from these studies are presented, too.

Light nuclei are few-body quantal systems and historically their spectra were the first to be studied experimentally.In a recent review,the existing experimental data from the stable N=Z dou-bly-odd nuclei and spectroscopic studies have been discussed,as well as the β decay of the corresponding isobaric multiplets[1].

. - 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.

Excited states in 10 B were populated with the 10 B ( p, p ' gamma ) 10 B * reaction at 8.5 MeV and their gamma decay was investigated via coincidence gamma-ray spectroscopy. The emitted gamma rays were measured using large-volume LaBr3Ce and CeBr3 detectors placed in anti-Compton shields. This allowed the observation of weak gamma-ray transitions, such as the M 3 transition between the J pi , T = 0+, 1 isobaric analog state (IAS) and the J pi , T = 3+, 0 ground state and the E 2 transition between the J pi , T = 2+1 , 0 state and the IAS, i.e., performing measurements of branching ratios at the level of lambda >= 10-4. For the first time in 10 B, the competing M 1 and M 3 transitions from the decay of the IAS have been observed in a gamma 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 10 B, and are in reasonable agreement with the observed branching ratios and reduced transition probabilities.

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.

The excited states of unstable ^{20}O were investigated via γ-ray spectroscopy following the ^{19}O(d,p)^{20}O reaction at 8  AMeV. By exploiting the Doppler shift attenuation method, the lifetimes of the 2_{2}^{+} and 3_{1}^{+} states were firmly established. From the γ-ray branching and E2/M1 mixing ratios for transitions deexciting the 2_{2}^{+} and 3_{1}^{+} states, the B(E2) and B(M1) were determined. Various chiral effective field theory Hamiltonians, describing the nuclear properties beyond ground states, along with a standard USDB interaction, were compared with the experimentally obtained data. Such a comparison for a large set of γ-ray transition probabilities with the valence space in medium similarity renormalization group ab initio calculations was performed for the first time in a nucleus far from stability. It was shown that the ab initio approaches using chiral effective field theory forces are challenged by detailed high-precision spectroscopic properties of nuclei. The reduced transition probabilities were found to be a very constraining test of the performance of the ab initio models.

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 existing experimental data for the γ decay of the stable N=Z doubly-odd nuclei and the β decay of the corresponding isospin multiplets is reviewed. The structure of the lightest nuclei with masses A≤14 is used to test and constrain ab initio nuclear theories. Most of the data were obtained in the second half of the last century and, in some cases, lack the needed precision for comparison with theoretical calculations. Recent spectroscopic studies in the lightest doubly-odd N = Z nuclei are discussed, as well as open problems related to the understanding of their structures and ideas for future experiments.

The gamma beam system under construction at the ELI-NP facility in Romania is projected to give the nuclear physics community access to an experimental system providing a high-intensity, narrow bandwidth photon beam at variable energy. With high-efficiency detector systems in place, the experimental programme will have a strong potential for in-depth studies of rare stable isotopes originating from the astrophysical p -process. In particular, the neutron detection systems are already implemented through a dedicated 3 He long neutron counter array, called ELIGANT-TN, that is completed and in use. In this mini-review, we will give a summary of the current status of existing ( γ , n) cross-section data, as well as the methods to obtain them, and highlight the future potential to expand and improve such data using the ELI-NP instrumentation and beam-lines.

Photo-nuclear reactions of light nuclei below a mass of $A=60$ are studied experimentally and theoretically by 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 gamma-ray beam produced by laser Compton scattering, will be applied to measure the photo-absorption cross sections and the 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 type models, a large-scale shell model, and ab initio models, will be employed to predict the photo-nuclear reactions. The uncertainty in the model predictions will be evaluated from the discrepancies between the model predictions and the experimental data. The data and the predictions will be implemented in a 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.

published or not.The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

The new facility, Extreme Light Infrastructure – Nuclear Physics (ELI-NP), is a combined laser-gamma nuclear physics research facility currently undergoing its final implementation stages in Măgurele near Bucharest, Romania. It already hosts two fully-operational 10 PW laser arms and, by 2023, it will also house a γ-beam system based on laser Compton backscattering, capable of delivering a high-brilliance, low-energy beam at E γ ≲ 19.5 MeV. Owing to this unique laser-gamma instrumentation combination, several types of experiments will be possible at ELI-NP, including high precision nuclear resonance fluorescence (NRF) experiments. In this case, the main γ-beam detection system for performing NRF studies at ELI-NP is represented by the ELI Array of DEtectors (ELIADE), featuring eight high-purity germanium (HPGe) segmented clover detectors. The current work presents the characteristics of two of the ELIADE detectors, including their photopeak detection efficiency, energy resolution, and peak-to-total ratio measured using γ-ray sources, as well as the timing performance obtained via in-beam measurements. For these latter detector tests, 130La was populated via the fusion evaporation reaction 121Sb(12C,3n)130La using a beam energy of 53 MeV at the Horia Hulubei National Institute of Physics and Nuclear Engineering (IFIN-HH), also located in Măgurele. Herein, we report on the results of the ^130La linear polarization measurements taken using the ELIADE detectors as Compton polarimeters. The results obtained from the in-beam experiment were compared to several already published works and we present new information on the transition multipolarity in 130La.

A promising technique for g-factor measurements on short-lived nuclear states utilises the hyperfine fields of free ions in vacuum. To fully utilise this technique the hyperfine interaction must be modelled based on atomic structure calculations. Atomic structure calculations were performed using the most recent release of the General Relativistic Atomic Structure Package, and Monte-Carlo simulations of atomic-decay cascades in highly charged ions were developed. The simulations were used to fit experimental data on excited 56Fe ions recoiling in vacuum with a view to determining the first-excited state g factor, g(21+), of 56Fe.

The magnetic moment of the isomeric state of the neutron-rich ^75Cu nucleus was measured using a highly spin-aligned beam produced via a two-step reaction scheme. In the experiment carried out at the BigRIPS at RIBF, we achieved to produce spin alignment reaching 30% by employing the one-proton removal from ^76Zn to produce ^75Cu. In the magnetic moment measurement, a method of time-differential perturbed angular distribution (TDPAD) was employed. Precession of the isomeric state with spin parity of 3/2^− was clearly observed with significance larger than 5σ in the TDPAD spectrum. The magnetic moment of the isomeric state of ^75Cu was determined to be μ = 1.40(6)μ_N.

The gyromagnetic factor of the low-lying E=251.96(9)  keV isomeric state of the nucleus ^{99}Zr was measured using the time-dependent perturbed angular distribution technique. This level is assigned a spin and parity of J^{π}=7/2^{+}, with a half-life of T_{1/2}=336(5)  ns. The isomer was produced and spin aligned via the abrasion-fission of a ^{238}U primary beam at RIKEN RIBF. A magnetic moment |μ|=2.31(14)μ_{N} was deduced showing that this isomer is not single particle in nature. A comparison of the experimental values with interacting boson-fermion model IBFM-1 results shows that this state is strongly mixed with a main νd_{5/2} composition. Furthermore, it was found that monopole single-particle evolution changes significantly with the appearance of collective modes, likely due to type-II shell evolution.