Experimental Nuclear Data Research Articles

Energy Levels of Light Nuclei A=13

Experimental nuclear spectroscopic data are evaluated for the 7 known nuclides of mass 13 (Li, Be, B, C, N, O, F). Detailed information is compiled and presented for each reaction and decay experiment. The results are combined and used to provide a set of recommended values that include level energies, spins and parities, half-lives of levels, decay branching ratios, and other nuclear properties. This work supersedes the earlier work by Fay Ajzenberg-Selove (1990Aj01) published in Nuclear Physics A 523 (1991) 1. Earlier reviews were published in (1986Aj01, 1981Aj01, 1976Aj04, 1970Aj04, 1959Aj76).

Excitation functions of (n, p) reactions for the production of iodine isotopes used in medical applications

The cross sections of 124Xe (n, p)124I, 125Xe (n, p)125I, 126Xe (n, p)126I, 128Xe (n, p)128I, 129Xe (n, p)129I, 130Xe (n, p)130I, 131Xe (n, p)131I, 132Xe (n, p)132I, 133Xe (n, p)133I, 134Xe (n, p)134I and 135Xe (n, p)135I for production of iodine isotopes were calculated at neutron energy ranges between 1 and 20 MeV with the help of three computer nuclear codes (EMPIRE 3.2.3, ALICE-ASH and TALYS 1.95). Furthermore, the cross sections were calculated by the empirical formula derived in some previous studies at 14.5 MeV. The previous calculated data from the evaluated data from the Evaluated Nuclear Data File (ENDF), such as ENDF/B-VIII.0; JEFF-3.3; ROSFOND-2010; CENDL-3.2; JENDL-4.0; JENDL-5.0; and TENDL-2021, as well as the experimental nuclear reaction cross-section data (EXFOR) about the above reactions, have been collected. In general, the calculated results by computer codes are in good agreement when compared with earlier empirical formulas, the measured values in the EXFOR library, and the evaluated data (ENDF/B-VIII.0; JEFF-3.3; JENDL-4.0; JENDL-5.0; ROSFOND-2010; CENDL-3.2; and TENDL-2021) with some exceptional.

Photon strength functions and nuclear level densities: invaluable input for nucleosynthesis.

The pivotal role of nuclear physics in nucleosynthesis processes is being investigated, in particular the intricate influence of photon strength functions (PSFs) and nuclear level densities (NLDs) on shaping the outcomes of the i-, r- and p-processes. Exploring diverse NLD and PSF model combinations uncovers large uncertainties for (p,[Formula: see text]), (n,[Formula: see text]) and ([Formula: see text],[Formula: see text]) rates across many regions of the nuclear chart. These lead to potentially significant abundance variations of the nucleosynthesis processes and highlight the importance of accurate experimental nuclear data. Theoretical insights and advanced experimental techniques lay the ground work for profound understanding that can be gained of nucleosynthesis mechanisms and the origin of the elements. Recent results further underscore the effect of PSF and NLD data and its contribution to understanding abundance distributions and refining knowledge of the intricate nucleosynthesis processes. This article is part of the theme issue 'The liminal position of Nuclear Physics: from hadrons to neutron stars'.

Nuclear Structure and Decay Data for A=165 Isobars

Experimental nuclear spectroscopic data are compiled and evaluated for 18 known nuclides of mass 165 (Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Re, Os, Ir, Pt). Detailed information is presented for each reaction and decay experiment. Combining all the available data, recommended values are provided for energies, spins and parities, and half-lives of levels, with energies, branching ratios and multipolarities of γ radiations, and characteristics of β and α radiations in radioactive decays. 165Dy, 165Ho, 165Er, 165Tm, 165Yb, 165Lu and 165Hf are among the most extensively studied nuclides via decay and high-spin gamma-ray spectroscopy measurements, followed by limited data for 165Tb, 165Ta, 165W, 165Re, and 165Os. No excited states have yet been identified in 165Sm, 165Gd, and 165Pt, while for 165Eu and 165Ir, information is available for only the g.s. and an isomer, but with no γ rays. This work supersedes earlier evaluation of A=165 nuclides by 2006Ja09.

Nuclear Structure and Decay Data for A=76 Isobars

The experimental nuclear spectroscopic data for known nuclides of mass number 76 (Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Br, Kr, Rb, Sr, Y) have been evaluated and presented together with Adopted properties for levels and γ rays. With the exception of structure data for 76Ga nucleus, significant new data have been incorporated for all the other nuclides of A=76 since the previous 1995 update in ENSDF database and NDS publication 1995Si03. No data are yet available for excited states in 76Fe, 76Cu and 76Y. Decay scheme characteristics for the decay of 76Co, 76Ni, and 76Y are unknown while those for decays of 76Cu and 76Sr seem incomplete. For 76Ni, very little structure data are available, and for 76Ga and 76As, only low-spin (J<4 or so) information is available. This work supersedes the data presented in the previous (1995Si03) NDS evaluation of A=76.

Spectroscopy of neutron-rich nuclei produced by multinucleon transfer reactions at KISS

Properties such as lifetimes and masses of neutron-rich nuclei are key parameters for elucidating the astrophysical rapid neutron capture process (r-process). Due to the lack of experimental nuclear data in the relevant extremely neutron-rich region, especially near and above N = 126, the predictions of theoretical nuclear models are crucial for simulating r-process nucleosynthesis. Experimental studies of the properties and structures of neutron-rich nuclei from near the β stability line up to the r-process path provide important inputs to these theoretical models, improving the accuracy of predictions for the nuclear properties involved in the rprocess. We are developing the KEK Isotope Separation System (KISS) at the RIKEN RIBF facility to produce and separate these nuclei to perform spectroscopy experiments. The nuclei of interest are produced by multinucleon transfer reactions, which have been recently attracting renewed interest as they provide a way to access neutron-rich nuclei that are difficult to produce by other methods such as complete fusion or fragmentation. We have performed nuclear and laser spectroscopy, lifetime and mass measurements of neutron-rich nuclei of refractory elements near the N = 126 region using 198,natPt, natTa, natW, and natIr targets irradiated with 136Xe beams. We also extend our spectroscopic studies into the neutron-rich actinide region using 238U beams. This paper introduces the KISS facility and provides an overview of the nuclear spectroscopy experiments carried out there. We also introduce the KISS-1.5 project, which was started in FY2024 to further extend the research into the neutron-rich region.

Nuclear Structure and Decay Data for A=167 Isobars

Experimental nuclear spectroscopic data are compiled and evaluated for 17 known nuclides of mass 167 (Sm, Eu, Gd, Tb, Dy, Ho, Er Tm, Yb, Lu, Hf, Ta, W, Re, Os, Ir, Pt), 23 years after the previous full evaluation by 2000Ba65. Detailed information is presented for each reaction and decay experiment. Combining all the available data, recommended values are provided for energies, spins and parities, and half-lives of levels, with energies, branching ratios and multipolarities of γ radiations, and characteristics of β and α radiations in radioactive decays. The α decays of A=171 nuclei to A=167 daughters are included in this work, while for α decays of A=167 nuclei to A=163 daughters, consult Nuclear Data Sheets (2010Re03) or the ENSDF database for A=163. 167Er, 167Tm, 167Yb, 167Lu and 167Ta are among the most extensively studied nuclides via decay and high-spin gamma-ray spectroscopy measurements, followed by 167Ho, 167Hf, 167W, and 167Os. Information for excited states in 167Dy, 167Re, and 167Ir are limited; no excited states have yet been identified in 167Sm, 167Eu, 167Gd, 167Tb and 167Pt, with the ground-state half-life of 167Sm remaining unknown. This work supersedes the earlier evaluation of A=167 nuclei by 2000Ba65.

A study on nuclear binding energy and beta decay energy using deep neural networks

The Artificial Neural Network (ANN) is one of the innovative methods for predicting the structural and dynamic properties of atomic nuclei. In this work, we employed machine learning based on the Deep Neural Network (DNN) technique to find the ground state binding energy and beta decay energy of various nuclei. 3560 experimental nuclear data sets have been used for training and validating the DNN model. Neutron number (N), proton number (Z), the pairing term (δ), a magic number greater than or equal to N and Z, asymmetry factor (a) and promiscuity factor (P) are used as input parameters. The Rectified Linear Unit (ReLU) function and Mean Absolute Error (MAE) are used as activation and Loss functions for the training process. We perform the predictions of ground state binding energy per nucleon and beta decay energies in Zinc and Promethium isotopes using the DNN model, which is in good agreement with experimental results.

Nuclear Structure and Decay Data for A=44 Isobars

Experimental nuclear spectroscopic data are evaluated for 12 known nuclides of mass number A=44 (Si, P, S, Cl, Ar, K, Ca, Sc, Ti, V, Cr, Mn). Detailed evaluated information are presented for each reaction and decay. Recommended values combining all available data are provided for all spectroscopic properties of each level, γ-ray, and decay radiation. No excited states have yet been identified in 44Si, 44P, 44Cr, and 44Mn. Information for excited states in 44Cl and 44V are limited. Nuclides of 44S, 44Ar and 44K have been studied via only a few reactions and decays, while 44Ca, 44Sc and 44Ti are the most investigated nuclides through various reactions and decays. Evaluators note that the half-life of the g.s. of 44S has been measured independently, with fairly good statistics, in three references, most precise being 100 ms 1 by 2004Gr20, but this value is in disagreement with the values of 125.5 ms 25 and 119 ms 6 by 2022Tr03, and 123 ms 10 by 1995So03. We adopted the unweighted average of this discrepant dataset. Another outstanding issue is that of the β+-delayed proton decay of 44Cr g.s. to 44V, where the T=2, 0+ IAS state in 44V is expected to be strongly populated by a superallowed β transition, but has not been definitely identified as discussed in detail by 2020Fu05. A detailed study of 44Cr decay is required to unravel the status of the T=2, 0+ IAS state in 44V. This work supersedes earlier ENSDF evaluations of A=44 by 2011Ch39 and 1999Ca45.

Nuclear Structure and Decay Data for A=71 Isobars

Experimental nuclear spectroscopic data are evaluated for 12 known nuclides of mass number=71 (Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Br, Kr). Detailed compiled and evaluated information is presented for each reaction and decay experiment. The β−n decay of 72Co to 71Ni is included in this work, while for β−n decay of 71Co to 70Ni, consult Nuclear Data Sheets for A=70 (2016Gu11) or the ENSDF database for 70Ni. Combining all the available data, recommended values are provided for energies, spins and parities, and half-lives of levels, with energies, branching ratios and multipolarities of γ radiations, and characteristics of β and α radiations in radioactive decays. Excited-states have not yet been identified in 71Mn, 71Fe, and 71Kr, with the ground-state half-life remaining unknown only for 71Mn; data for excited states in 71Co and 71Ni are very limited; 71Ga, 71Ge and 71As are the most extensively studied nuclides via various reactions and decays, followed by 71Cu, 71Zn, 71Se, and 71Br, however, except for 71Ge, the decay schemes of all other nuclides are considered as incomplete due to a large gap between the decay Q-value and the highest observed level. This work supersedes earlier evaluations of A=71 by 2011Ab01.

STEREO neutrino spectrum of 235U fission rejects sterile neutrino hypothesis.

Anomalies in past neutrino measurements have led to the discovery that these particles have non-zero mass and oscillate between their three flavours when they propagate. In the 2010s, similar anomalies observed in the antineutrino spectra emitted by nuclear reactors have triggered the hypothesis of the existence of a supplementary neutrino state that would be sterile, that is, not interacting by means of the weak interaction1. The STEREO experiment2-6 was designed to investigate this conjecture, which would potentially extend the standard model of particle physics. Here we present an analysis of the full set of data generated by STEREO, confirming observed anomalies while rejecting the hypothesis of a light sterile neutrino. Installed at the Institut Laue-Langevin (ILL) research reactor, STEREO accurately measures the antineutrino energy spectrum associated to the fission of 235U. The segmentation of the detector and its very short distance to the compact core are crucial properties of STEREO for our analysis. The measured antineutrino energy spectrum suggests that anomalies originate from biases in the nuclear experimental data used for the predictions7,8. Our result supports the neutrino content of the standard model and establishes a new reference for the 235U antineutrino energy spectrum. We anticipate that this result will allow progress towards finer tests of the fundamental properties of neutrinos but also to benchmark models and nuclear data of interest for reactor physics9,10 and for observations of astrophysical or geoneutrinos11,12.

Dependence of (n,γ)−(γ,n) equilibrium r -process abundances on nuclear physics properties

In most $r$-process expansions, the dominant nuclear evolution occurs in an $(n,\ensuremath{\gamma})\text{\ensuremath{-}}(\ensuremath{\gamma},n)$ equilibrium in which nuclei rapidly exchange neutrons but change charge much more slowly by beta decay. Freeze-out from this equilibrium shapes the final abundances but does not significantly alter the overall global abundance pattern; therefore, it is important to understand the details of $(n,\ensuremath{\gamma})\text{\ensuremath{-}}(\ensuremath{\gamma},n)$ equilibrium both because it is the main evolution phase that determines the final abundance pattern and because it is the starting point for the freeze-out. Through use of a simple but realistic phenomenological nuclear physics model, we show that isotopic abundances versus neutron number in $(n,\ensuremath{\gamma})\text{\ensuremath{-}}(\ensuremath{\gamma},n)$ equilibrium are well approximated as Gaussians. Nuclear pairing causes isotopic abundances to alternate between two Gaussians, and shell effects cause the isotopic abundances to shift from one Gaussian to another when the neutron number crosses a magic number. More complex neutron-separation energy curves versus mass number can be generated by adding a spike function to a linearly declining curve. In such a case, the equilibrium abundance curve jumps from one Gaussian to another for each added spike. Insights from our model can help shed light on how detailed theoretical or experimental nuclear data affect $r$-process nucleosynthesis during the $(n,\ensuremath{\gamma})\text{\ensuremath{-}}(\ensuremath{\gamma},n)$ equilibrium phase.

Nuclear Structure and Decay Data for A=31 Isobars

Experimental nuclear spectroscopic data are evaluated for 11 known nuclides of mass 31 (F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K). Detailed evaluated information is presented for each reaction and decay experiment. Combining all the available data, recommended values are provided for energies, spins and parities, and half-lives of levels, with energies, branching ratios and multipolarities of γ radiations, and characteristics of β and α radiations in radioactive decays. 31P is the most extensively studied one among all nuclides via various reactions and decays, followed by 31S, 31Si, 31Mg and 31Al. Information for excited states in 31Ne, 31Na, 31Cl, 31Ar and 31K are limited; no excited states have yet been identified in 31F, even its ground-state half-life is unknown. Significant new data have become available for the structure of 31S, with its relevance to astrophysical applications. This work supersedes the earlier evaluation of A=31 by 2013Ou01, with literature cutoff date of Feb 15, 2013.

Performing Bayesian Analyses With AZURE2 Using BRICK: An Application to the 7Be System

Phenomenological R-matrix has been a standard framework for the evaluation of resolved resonance cross section data in nuclear physics for many years. It is a powerful method for comparing different types of experimental nuclear data and combining the results of many different experimental measurements in order to gain a better estimation of the true underlying cross sections. Yet a practical challenge has always been the estimation of the uncertainty on both the cross sections at the energies of interest and the fit parameters, which can take the form of standard level parameters. Frequentist (χ2-based) estimation has been the norm. In this work, a Markov Chain Monte Carlo sampler, emcee, has been implemented for the R-matrix code AZURE2, creating the Bayesian R-matrix Inference Code Kit (BRICK). Bayesian uncertainty estimation has then been carried out for a simultaneous R-matrix fit of the 3He (α,γ)7Be and 3He (α,α)3He reactions in order to gain further insight into the fitting of capture and scattering data. Both data sets constrain the values of the bound state α-particle asymptotic normalization coefficients in 7Be. The analysis highlights the need for low-energy scattering data with well-documented uncertainty information and shows how misleading results can be obtained in its absence.

Onset of Electron Captures and Shallow Heating in Magnetars

The loss of magnetic pressure accompanying the decay of the magnetic field in a magnetar may trigger exothermic electron captures by nuclei in the shallow layers of the stellar crust. Very accurate analytical formulas are obtained for the threshold density and pressure, as well as for the maximum amount of heat that can be possibly released, taking into account the Landau–Rabi quantization of electron motion. These formulas are valid for arbitrary magnetic field strengths, from the weakly quantizing regime to the most extreme situation in which electrons are all confined to the lowest level. Numerical results are also presented based on experimental nuclear data supplemented with predictions from the Brussels-Montreal model HFB-24. This same nuclear model has been already employed to calculate the equation of state in all regions of magnetars.

Maxwellian-averaged cross section of 181Ta (n,γ) reaction and its astrophysical implications

The neutron-capture and Maxwellian-averaged cross sections of 181Ta(n,γ) reaction have been computed making use of the TALYS code. Two main inputs of the TALYS calculation, nuclear level density (NLD) and radiative strength function (RSF), are calculated within a recent microscopic model that takes into account the exact thermal pairing plus independent-particle model and collective excitations within the phonon-damping model. A good agreement between the calculated and experimental NLD and RSF data of 182Ta was found, confirming the goodness of the microscopic nuclear model used. As the result, the deduced neutron-capture and Maxwellian-averaged cross sections of 181Ta(n,γ) reaction also agree reasonably well with the experimental and recommended data across the measured energy range. The impact of the predicted cross sections on the tantalum production in the slow neutron-capture process (s-process) is then studied by employing a recent version of FRUITY stellar evolutionary models in which the effect of magnetic fields is newly implemented. By calculating the isotopic composition ratios within the FUNS code, we obtain a slight depletion of tantalum as compared to the recommended data. The variation between the calculated and reference tungsten isotopic ratios in presolar stardust silicon carbide (SiC) grains is found to be negligible, as expected. However, the capability of our theoretical model to reproduce experimental nuclear data will allow us to investigate in detail the s-process branching points at 181W and 185W, for which experimental data from direct measurements are still unavailable.

The ADAMO project for the dark matter directionality approach

Anisotropic scintillators can offer a unique possibility to exploit the so-called directionality approach to investigate the presence of those Dark Matter (DM) candidates inducing nuclear recoils. Their use can overcome the difficulty of detecting extremely short nuclear recoil tracks. In this paper, we present recent measurements performed on the anisotropic response of a ZnWO4 crystal scintillator to nuclear recoils in the framework of the ADAMO project. The anisotropic features of the ZnWO4 crystal scintillators were initially measured with [Formula: see text] particles; those results have also been confirmed by the additional measurements presented here. The experimental nuclear recoil data were obtained using a neutron generator at ENEA-Casaccia and neutron detectors to tag the scattered neutrons; in particular, the quenching factor values for nuclear recoils along different crystallographic axes have been determined for three different neutron scattering angles (i.e. nuclear recoils energies). The anisotropy of the light response for nuclear recoils in the ZnWO4 crystal scintillator has been determined at 5.4 standard deviations. These results open the possibility to realize a pioneering experiment to investigate the above-mentioned DM candidates by means of the directionality.

The Impact of Nuclear Physics Uncertainties on Interpreting Kilonova Light Curves

Recently, analysis of the optical counterpart AT2017gfo to the gravitational wave-detected neutron star merger GW170817 has suggested a promising resolution of a long-standing debate on neutron star mergers as a source of some of the heaviest elements. However, making quantitative progress in these areas requires an accounting of the uncertainties in different aspects of physics, which is input into simulations of merging compact objects and their associated phenomena, remarkably rapid neutron capture nucleosynthesis. We investigate the uncertainties from the nuclear inputs to rapid neutron capture nucleosynthesis calculations combining different theoretical nuclear mass models, spontaneous fission rates, and fission daughter product distributions on top of the experimental nuclear data. We report that such nuclear physics uncertainties typically generate at least one order of magnitude uncertainty in the nuclear heating, which leads to uncertainties in the bolometric luminosity and the inferred mass of r-process material from the kilonova light curve.

The Nuclear Matter Density Functional under the Nucleonic Hypothesis

A Bayesian analysis of the possible behaviors of the dense matter equation of state informed by recent LIGO-Virgo as well as NICER measurements reveals that all the present observations are compatible with a fully nucleonic hypothesis for the composition of dense matter, even in the core of the most massive pulsar PSR J0740+6620. Under the hypothesis of a nucleonic composition, we extract the most general behavior of the energy per particle of symmetric matter and density dependence of the symmetry energy, compatible with the astrophysical observations as well as our present knowledge of low-energy nuclear physics from effective field theory predictions and experimental nuclear mass data. These results can be used as a null hypothesis to be confronted with future constraints on dense matter to search for possible exotic degrees of freedom.

Determination of Energy Spectra By Using Proper Quantization Rule of Woods-Saxon Potential

In this study, the energy spectra of Schrodinger equation for non-zero l values considering Woods Saxon potential (WSP) is calculated using proper quantization rule, then the binding energies (BE) of random light nuclei is obtained and the optimized potential parameters such as potential depth (V0) and surface thickness (a) are found. In order to calculate the energy levels of the nuclei with WSP, the PQR method was used, which has not been considered before. In quantum mechanics, the exact solution of energy systems, momentum, and quantum states can be found using the proper quantization rule(PQR) method.Using the Matlab calculation program, we have achieved numerical values of the energy spectrum for random light nuclei and compared the result with the experimental Nuclear Data Center (NDC) values. In addition, we found potential depth and surface thickness for four light nuclei. Correlations between the light nuclei show the facts about the nuclear structure characteristics, origin, and energies of these nuclei. Pearson’s correlation coefficient is accepted as the most common correlation coefficient. According to the values of Pearson correlation coefficients, it is observed that there is a significant positive correlation between the nucleons examined. Finally, we plot the E-V0-a diagrams for those values to optimize and provide the appropriate coefficients. It is shown that there is a good agreement between the results of this work and experimental values.