Low-lying states of ^94Zr were investigated via low-energy multi-step Coulomb excitation. From the measured γ-ray yields, 16 reduced E2 transition probabilities between low-spin states were determined, together with the spectroscopic quadrupole moments of the 2_1,2^+ states. Based on this information, for the first time in the Zr isotopic chain, the shapes of the 0_1,2^+ states including their deformation softness were inferred in a model-independent way using the quadrupole sum rules approach. The ground state of ^94Zr possesses a rather diffuse shape associated with a spherical configuration, while the 0_2^+ state is triaxial tending towards oblate and more strongly deformed. The observed features of shape coexistence in ^94Zr are consistent with both Monte-Carlo shell-model predictions and IBM-CM calculations, and provide model-independent constraints on the shape character assigned in the IBM-CM to the intruder configuration in ^92–96Zr.

Low-energy multi-step Coulomb excitation measurements have been performed to study the structure of low-lying excitations in the zirconium isotopes, which are particularly interesting as, in recent years, evidence has come to light that they are excellent cases for exhibiting shape evolution and shape coexistence. In order to provide definitive information on the shapes of the low-lying states of 94,96 Zr, two Coulomb excitation experiments were performed at INFN-LNL using γ-ray spectrometers coupled with the heavy-ion detector array SPIDER. In the 94 Zr experiment SPIDER was coupled to the resident array GALILEO, based on HPGe detectors, and 6 lanthanum bromide scintillators. In the 96 Zr experiment the γ-ray tracking spectrometer AGATA was used in conjunction with SPIDER. The information obtained from the measured yields for γ-particle coincidences indicates the presence of coexisting shapes in these nuclei and will allow for an in-depth comparison with theoretical predictions.

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.

. - 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.

One-neutron stripping process between ^6 Li and ^209 Bi was studied at 28, 30, and 34 MeV using the in-beam γ -ray spectroscopy method. The γ – γ coincident analysis clearly identified two γ -rays feeding the ground and long-lived isomeric states, which were employed to determine the cross section. The one-neutron stripping cross sections were similar to the cross sections of complete fusion in the ^6 Li+ ^209 Bi system, but the one-neutron stripping cross sections decreased more gradually at the sub-barrier region. A coupled-reaction-channel calculation was performed to study the detailed reaction mechanism of the one-neutron stripping process in ^6 Li. The calculations indicated that the first excited state of ^5 Li is critical in the actual one-neutron transfer mechanism, and the valence proton of ^209Bi can be excited to the low-lying excited state in ( ^6Li , ^5Li ) reaction, unlike in the (d,p) reaction.

The 6Li+89Y experiment was conducted at the Legnaro National Laboratory in Italy to explore the influence of breakup and transfer reactions on the fusion process induced by the weakly bound projectiles. Due to the competition between neutron and proton evaporation, complete and incomplete fusion might produce identical residues, leading to the difficulties in identification of different reaction process. In this work, the High-Purity-Germanium (HPGe) detector array (GALILEO) was employed to measure γ rays, and the silicon detector array (EUCLIDES) was utilized to capture light charged particles. Exclusive measurements of prompt γ rays from residuals with various light charged particles at an energy near the Coulomb barrier are reported. In the p−γ coincident measurements, observed 91Nb, 92Nb, and 93Nb is consideredfrom neutron evaporation channel in complete fusion reaction, and 90Y is generated through 1n stripping reaction. A two-step, breakup followed by fusion, in case of the capture of α is inferred to be the dominant mechanism to yield the 92Nb and 91Nb in the deutron coincident exclusive measurement.

Neutron dark decays have been suggested as a solution to the discrepancy between bottle and beam experiments, providing a dark matter candidate that can be searched for in halo nuclei. The free neutron in the final state following the decay of ^{6}He into ^{4}He+n+χ provides an exceptionally clean detection signature when combined with a high efficiency neutron detector. Using a high-intensity ^{6}He^{+} beam at Grand Accélérateur National d'Ions Lourds, a search for a coincident neutron signal resulted in an upper limit on a dark decay branching ratio of Br_{χ}≤4.0×10^{-10} (95% C.L.). Using the dark neutron decay model proposed originally by Fornal and Grinstein, we translate this into an upper bound on a dark neutron branching ratio of O(10^{-5}), improving over global constraints by one to several orders of magnitude depending on m_{χ}.

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.

In the last two decades, several unique phenomena in triaxially deformed nuclei, such as chiral doublet bands and wobbling motion have been revealed. Up to now, there are still many open questions which require further experimental and theoretical studies. To explore the collective motion in 131Ba, an experiment was performed using the XTU Tandem accelerator in the Legnaro laboratory, Italy. High-spin states of 131Ba have been populated via the heavy-ion fusion-evaporation 122Sn(13C, 4n) reaction. γ-rays, charged particles and neutrons emitted from the residues were detected by the GALILEO array, EUCLIDES silicon ball, and the Neutron Wall, respectively. A total of 1.2\begin{document}$ \times $\end{document}109 triple- or higher-fold events were collected by the GALILEO data acquisition system. The γ-γ-γ coincidence events were sorted into a three-dimensional histogram (cube) and the analysis was carried out with the RADWARE and GASPWARE software packages.Through analysis of the coincidences between γ-rays, the most comprehensive level schemes of 131Ba to date was deduced from the present work. The extended level-scheme consists of 15 rotational bands, and newly observed transitions are marked in red. Three nearly degenerate pairs of doublet bands (Band 3–8) are identified in 131Ba. Two pairs of chiral doublets (Band 3–6) with configuration \begin{document}$ {\textit{\pi}}h_{11/2}(g_{7/2},d_{5/2}){\otimes}{\nu}h_{11/2} $\end{document} are interpreted as a set of pseudospin-chiral quartet bands. The quartet bands are fed by another pair of chiral doublet bands (Band 7–8) built on a \begin{document}$ {\textit{\pi}}h^2_{11/2}{\otimes}{\nu}h_{11/2} $\end{document} configuration via a series of enhanced E1 transitions. We extracted the energy displacement δE and the B(E1)/B(E2) branching ratios between the positive-parity band 3 and the negative-parity band 7 in 131Ba and in comparison with those in 124Ba, 224Th, 133Ce and 135Nd. The energy displacement δE and the B(E1)/B(E2) branching ratios in 131Ba are comparable with those in 124Ba but deviate appreciably from those in 224Th which has been reported to have stable octupole deformation. The results indicate the existence of octupole correlations in 131Ba without stable octupole deformation. A new rotational band (Band 10) discovered in the low-spin region exhibits a level structure similar to a wobbling band. Assuming it as a wobbling band, the wobbling frequency was extracted and compared with other reported wobbling bands in the neighboring nuclei. The wobbling frequency of this band decreases with increasing angular momentum, and even exhibits negative value at the highest spin. Considering that the wobbling phonon should contribute a positive amount to the excitation energy, this band is unlikely to be explained by this mechanism. The band may originate from other collective excitation mechanisms such as γ vibration. The newly identified rotational band (Band 9) composed of M1 transitions is tentatively assigned as a magnetic rotational band through a systematic analysis of the level structure. Finally, the configurations of other 4 bands, Band 12-15, are also suggested based on previous researches and the extracted quasiparticle alignments.

The complete and incomplete fusion cross sections for Li-6+Bi-209 were measured using the in-beam gamma-ray method around the Coulomb barrier. The cross sections of (deuteron captured) incomplete fusion (ICF) products were re-quantified experimentally for this reaction system. The results reveal that the ICF cross section is equivalent to that of complete fusion (CF) above the Coulomb barrier and dominant near or below the Coulomb barrier. A theoretical calculation based on the continuum discretized coupled channel (CDCC) method was performed for the aforementioned CF and ICF cross sections; the result is consistent with the experiments. The universal fusion function (UFF) was also compared with the measured CF cross section for different barrier parameters, demonstrating that the CF suppression factor is significantly influenced by the choice of potential, which can reflect both dynamic and static effects of breakup on the fusion process.

In this Letter we report on effects of nucleon-nucleon correlations probed in nucleon transfer reactions with heavy ions. We measured with high efficiency and resolution a complete set of observables for neutron transfer channels in the 206Pb & thorn; 118Sn system employing a large solid angle magnetic spectrometer, which allowed us to study a wide range of internuclear distances via a detailed excitation function. The coupled channel theory, based on an independent particle transfer mechanism, follows the experimental transfer probabilities for one- and two-neutron pick-up and stripping channels. The experimental two-neutron transfer cross sections indicate that in reactions between pair-vibrational (closed shell) and pair-rotational (open shell) nuclei, correlations manifest via pair-addition and pair-removal modes, which constitute one of the elementary modes of excitations in nuclei.

The ELIADE-y-ray spectrometer constructed at the Extreme Light Infrastructure Nuclear Physics (ELI-NP, Romania) is featured for Nuclear Resonance Fluorescent studies to be performed using a mono-energetical almost fully polarized-y-ray beam. This paper reports on the progress of implementation of ELIADE.

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

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.

We report a dedicated setup built in-house for the annealing of the HPGe clover detectors of the ELI-NP Array of DEtectors (ELIADE) γ-ray spectrometer, as well as the post-annealing testing of these detectors with the standard 60 Co & 152 Eu radioactive calibration sources employing conventional analog electronics. Both the design and assembly of the annealing setup were performed at the Extreme Light Infrastructure — Nuclear Physics (ELI-NP) facility, Măgurele, Romania. A `radiation damage annealing assembly kit' (NRK-200 unit) from the detector manufacturer Canberra is utilized in heating and controlling the temperature of the Ge crystals of the annealed detector. The vacuum inside the detector was maintained throughout the annealing process by constantly pumping the system using a turbo-molecular pumping station. The temperature of the germanium crystals, located inside a vacuum sealed chamber, of the detector and the vacuum level of this chamber were monitored throughout the annealing process, via both in-person observation and remote (online) monitoring. The Graphic User Interface (GUI) of an underlying LabVIEW script was utilized for running the monitoring process of the temperature and vacuum pressure values via a local network. To have the option of real-time online monitoring of the temperature, vacuum pressure, we coupled the web application Grafana with the Influx DB of the annealing data, as well as the backup time information of an Uninterruptible Power Supply (UPS) unit used in system.

This work aims at presenting an alternative approach to the long standing problem of the B(E2) values in Sn isotopes in the vicinity of the N=Z double-magic nucleus 100Sn, until now predominantly measured with relativistic and intermediate-energy Coulomb excitation reactions. The direct measurement of the lifetime of low-lying excited states in odd-even Sn isotopes provides a new and precise guidance for the theoretical description of the nuclear structure in this region. Lifetime measurements have been performed in 105Sn for the first time with the coincidence Recoil Distance Doppler Shift technique. The lifetime results for the 7/21+ first excited state and the 11/21+ state, 2+(104Sn) ⊗ν1g7/2 multiplet member, are discussed in comparison with state-of-the-art shell model and mean field calculations, highlighting the crucial contribution of proton excitation across the core of 100Sn. The reduced transition probability B(E2) of the 11/21+ core-coupled state points out an enhanced staggering with respect to the B(E2; 21+→01+) in the even-mass 104Sn and 106Sn isotopes.