Radioactive Nuclei Research Articles

Nuclear Dynamics and Reactions in the Ab Initio Symmetry-Adapted Framework

We review the ab initio symmetry-adapted (SA) framework for determining the structure of stable and unstable nuclei, along with related electroweak, decay, and reaction processes. This framework utilizes the dominant symmetry of nuclear dynamics, the shape-related symplectic [Formula: see text] symmetry, which has been shown to emerge from first principles and to expose dominant degrees of freedom that are collective in nature, even in the lightest species or seemingly spherical states. This feature is illustrated for a broad scope of nuclei ranging from helium to titanium isotopes, enabled by recent developments of the ab initio SA no-core shell model expanded to the continuum through the use of the SA basis and that of the resonating group method. The review focuses on energies, electromagnetic transitions, quadrupole and magnetic moments, radii, form factors, and response function moments for ground-state rotational bands and giant resonances. The method also determines the structure of reaction fragments that is used to calculate decay widths and α-capture reactions for simulated X-ray burst abundance patterns, as well as nucleon–nucleus interactions for cross sections and other reaction observables.

Detailed study of the eikonal reaction theory for the breakup of one-neutron halo nuclei

Background: One-neutron removal reactions are used to study the single-particle structure of unstable nuclei, and in particular the exotic halo nuclei. The Eikonal Reaction Theory (ERT) has been developed by Yahiro, Ogata and Minomo in Prog. Theor. Phys. 126, 167 (2011) to include dynamical effects, which are missing in the usual eikonal description of these reactions. Encouraging results have been obtained for total breakup cross sections in comparison to more elaborate reaction models. Purpose: We extend these comparisons to more differential breakup cross sections expressed as functions of the relative energy or parallel momentum between the core and halo neutron. Method: ERT predictions of these cross sections are compared to state-of-the-art calculations. Results: The hypotheses upon which the ERT is based are confirmed and their range of validity is made clearer. The actual ordering of the evolution operators {affects ERT differential} cross sections and a specific choice leads to excellent agreement with the reference calculation. Dynamical effects in the treatment of the neutron-target interaction can be significant in the parallel-momentum observable. Conclusions: The role of the different interactions in the dynamics of breakup reactions of one-neutron halo nuclei are better understood and improvements to the ERT are suggested.

Analysis methods and code for very high-precision mass measurements of unstable isotopes

We present a robust analysis code developed in the Python language and incorporating libraries of the ROOT data analysis framework for the state-of-the-art mass spectrometry method called phase-imaging ion-cyclotron-resonance (PI-ICR). A step-by-step description of the dataset construction and analysis algorithm is given. The code features a new phase-determination approach that offers up to 10 times smaller statistical uncertainties. This improvement in statistical uncertainty is confirmed using extensive Monte-Carlo simulations and allows for very high-precision studies of exotic nuclear masses to test, among others, the standard model of particle physics. Program summaryProgram Title: PI-ICR analysis softwareCPC Library link to program files:https://doi.org/10.17632/5jxkxbkkkr.1Developer's repository link:https://doi.org/10.5281/zenodo.4553515Licensing provisions: MITProgramming language: PythonNature of problem: Analysis software for the next-generation mass spectrometry technique PI-ICR for radioactive isotopes and isomers.Solution method: Using Jupyter notebooks in the Python programming language and libraries of the ROOT analysis framework, the full PI-ICR analysis from the raw data to the final mass value is presented. Furthermore, a new phase-determination approach is introduced offering up to ten times smaller statistical uncertainties on the same dataset compared to the state-of-the-art approaches that are based on X/Y projection fits [14]. This improvement was confirmed by extensive Monte-Carlo simulations.Additional comments including restrictions and unusual features:1.A new phase-determination approach is presented offering up to ten times smaller statistical uncertainties on the same dataset compared to state-of-the-art approaches.2.The code features a robust and precise cyclotron-frequency ratio determination based on simultaneous polynomial fitting with several advantages over the commonly used linear extrapolation.3.The use of Jupyter notebooks and Python allows for a cloud-based analysis on any device or operating system offering a web browser through services such as CERN's SWAN platform or Google Colab.4.The entire frequency determination is based on Bayesian analysis using unbinned maximum likelihood estimation.

Mechanism of collagen folding propagation studied by Molecular Dynamics simulations.

Collagen forms a characteristic triple helical structure and plays a central role for stabilizing the extra-cellular matrix. After a C-terminal nucleus formation folding proceeds to form long triple-helical fibers. The molecular details of triple helix folding process is of central importance for an understanding of several human diseases associated with misfolded or unstable collagen fibrils. However, the folding propagation is too rapid to be studied by experimental high resolution techniques. We employed multiple Molecular Dynamics simulations starting from unfolded peptides with an already formed nucleus to successfully follow the folding propagation in atomic detail. The triple helix folding was found to propagate involving first two chains forming a short transient template. Secondly, three residues of the third chain fold on this template with an overall mean propagation of ~75 ns per unit. The formation of loops with multiples of the repeating unit was found as a characteristic misfolding event especially when starting from an unstable nucleus. Central Gly→Ala or Gly→Thr substitutions resulted in reduced stability and folding rates due to structural deformations interfering with folding propagation.

The Cold Fusion Phenomenon – Nuclear Reactions in the CF Materials at Around Room Temperature

Since the discovery of nuclear reactions in PdDx alloys at around room temperature in 1989, there have been accumulated very many experimental data sets showing existence of nuclear reactions in solid materials composed of transition metals and occluded hydrogen isotopes (let us call them the CF materials, for short) resulting in various nuclear products such as neutrons, tritium, transmuted nuclei, and others accompanied with large excess energies at relatively low temperatures up to 1000°C (let us call these whole events the cold fusion phenomenon (CFP), for short). As the cause of these nuclear reactions in the CFP, we have to accept the existence of the interactions between nuclei in the CF material through the nuclear force (let us call this interaction the nuclear-force interaction, for short) recognized its existence in the nucleus in the nuclear physics. We can classify the CF materials, i.e. materials where CFP occurs, into three groups: (1) metallic material including transition-metal hydrides (e.g. NiHx, AuHx) and deuterides (e.g. PdDx, TiDx), (2) carbonic material including hydrogen graphite (HCx) and XLPE (cross-linked polyethylene) and (3) biological material including microorganisms, microbial cultures and biological tissues or organs. We will explain the characteristics of the CFP observed in each group in this paper. The nuclear reactions in the CF material gives rise to production of new particles from neutron, triton, and new nuclei with proton numbers Z up to 83 accompanying enormous excess energy. In addition to these events, there occurs the stabilization of unstable nuclei, including the decay-time shortening of radioactive nuclei, which is especially interesting to apply it to treat hazardous nuclear waste produced by the nuclear power plant. Finally, we give an overview of the CFP in relation to the solid state-nuclear physics and the solid state-nuclear chemistry where the nuclear-force interaction may play important roles to explain the riddles found but not given appropriate explanations in these old sciences hitherto.

Study of the Static and Dynamic Nuclear Properties and Form Factors for Some Magnesium Isotopes 29-34 Mg

Nuclear structure of 29-34Mg isotopes toward neutron dripline have been investigated using shell model with Skyrme-Hartree–Fock calculations. In particular nuclear densities for proton, neutron, mass and charge densities with their corresponding rms radii, neutron skin thicknesses and inelastic electron scattering form factors are calculated for positive low-lying states. The deduced results are discussed for the transverse form factor and compared with the available experimental data. It has been confirmed that the combining shell model with Hartree-Fock mean field method with Skyrme interaction can accommodate very well the nuclear excitation properties and can reach a highly descriptive and predictive power when investigating different nuclear configurations of stable and unstable nuclei.

Elastic scattering of light radioactive nuclei as studied with ECIS

Elastic scattering of light radioactive nuclei as studied with ECIS

The blue hue of einsteinium.

A complex containing the unstable isotope 254Es has been synthesized on a nanogram scale. Analysis of the fundamental bonding and spectroscopic characteristics of this einsteinium compound shows a blue shift of Es(iii) luminescence upon complexation, and the ligand serves as an antenna to sensitize the excited state.

An approach for performing resolved and unresolved resonance evaluation based on few or none experimental data available: Application to unstable and short-lived isotopes

Fluctuations in the neutron cross sections resulting from resonance structures have to be accounted for in the calculation of a nuclear system. Regardless of the approach used, deterministic or stochastic, the depression in the neutron flux due to the resonance effects in the cross section must be well understood for the purpose of providing a good understanding of the self-shielding effects and an accurate calculation of any nuclear system. The R-Matrix theory is the mechanism most appropriate to represent the resonance region providing a detailed description of the cross sections thru resonance parameters.The objective of this work is to present an alternative to generate resonance region evaluation on the basis of the R-matrix theory in the resolved and unresolved energy regions. The proposed methodology can be applied to situations where few or none experimental data are available such as the energy dependent neutron cross section. It leverages over the knowledge of information such as thermal cross section values, Westcott factor, resonance integral, coherent and incoherent scattering lengths, scattering radius, and more important, knowledge of average resonance parameters. The approach is demonstrated and validated with applications for an isotope with a well-known resonance evaluation, that is the 103Rh, and afterwards to an isotope with minimum experimental data available. The latter is the 156Eu isotope.

Progress on internal gas-jet target nuclear reaction at the HIRFL-CSR

Direct nuclear reactions induced by light ions, e.g., proton and alpha particles, have been investigated for about a century since the Geiger-Marsden experiment in 1908. It provides important information on nuclear structure and nuclear astrophysics. For instance, neutron skin thicknesses of nuclei determined by using proton and α elastic scattering play an important role in constraining the equation of state (EOS) of isospin asymmetric nuclear matter. These reactions were mostly conducted in direct kinematics, that is to say, the light-ion beam from accelerator interacts with a target made of the nuclei of interest. Obviously, such kinds of experimental investigations are limited to stable solid isotopes without active chemical property and radioactivity, due to the difficulty to make unstable targets. To test theoretical models developed from stable nuclei and explore new physical phenomenon on exotic nuclei, it is essential to investigate direct reactions on nuclei far from stability. As a result, experimental method based on inverse kinematics, namely active gas target technique, has been developed, where the unstable nuclei of interest produced by radioactive ion beam facilities collide with hydrogen and helium gases in a bubble chamber. The direct reactions are performed in inverse kinematics. One advantage is that low energy recoils at small center of mass angles can be measured easily at relatively large laboratory angles. However, this experimental method is insensitive to detect scattering recoils with energies of a few hundred keV, due to measurement based on gas detector. In recent years, a novel experimental method, namely study with stored beam in storage ring interacting with internal gas-jet target, has attracted much interest. It was proposed firstly for the exotic nuclei studied with light-ion induced reactions in storage rings (EXL) project. The technique is based on the internal gas-jet target instead of active gas target. It is an important supplementary experiential method for studying direct nuclear reactions induced by light ions, which is characterized by low-momentum sensitivity, high detection efficiency and low background. It is an ideal tool to study the isotopes with active chemical property and radioactivity. The cooler storage ring at the heavy ion research facility in Lanzhou (HIRFL-CSR) consists of a main cooler storage ring (CSRm) and an experimental cooler storage ring (CSRe). The two rings are connected by a radioactive ion beam line 2 (RIBLL2). The CSRe is equipped with an internal gas-jet target. As one of the existing facilities, the HIRFL-CSR provides an opportunity for performing in-ring direct nuclear reactions induced by light ions with the internal gas-jet target. Since 2016, a silicon strip detector compatibility with ultra-high vacuum in heavy-ion storage ring has been developed to build the in-ring direct nuclear reaction spectrometry at the HIRFL-CSR. A feasibility experiment on proton elastic scattering on 58Ni nuclei has been operated successfully by using the in-ring nuclear reaction spectrometry at the HIRFL-CSR. The nuclear matter distribution radius of 58Ni was extracted from measured differential cross sections at low momentum transfer. Proton elastic scattering experiment on 78Kr nuclei was also carried out to extract the nuclear matter radius at the beginning of 2021. In this paper, we report the development of in-ring direct nuclear reaction spectrometry at the HIRFL-CSR and corresponding experiments. Research plans in the (near) future, especially for measuring nuclear matter distribution radius of 133Cs, are also introduced.

Evolution of soft monopole mode in the even-even nickel isotopes Ni58–68

The finite amplitude method is implemented for covariant density functional theory with the point-coupling functional PC-PK1 for deformed nuclei. The giant monopole resonances for even-even nickel isotopes $^{58\text{--}68}\mathrm{Ni}$ are studied. The experimentally reported soft monopole mode, a distinct form of nuclear compressional mode, for the unstable nucleus $^{68}\mathrm{Ni}$ is well reproduced. The evolution of the soft monopole mode in neutron-rich nickel isotopes is shown. Microscopic analysis of the transition density shows that the soft monopole mode is dominated by neutron vibrations.

Knock-out interpretability

A detailed analysis of a nucleon-knockout experiment has put forward a methodological roadmap for overcoming ambiguities in the interpretation of the data — promising access to the nuclear wave functions in unstable nuclei.

Concentrations Assessment Of Radon Gas and Some Radioactive Nuclei For Some Region In Basra Governorate By CR-39 Detector

In this work, eighteen samples were studied distributed over different sites in Basra Governorate from southern Iraq. The CR- 39 nuclear trace detector technique was used to reach the results, which showed us, the radium concentrations ranged between (18.52 - 2.169) Becquerel / kg, the environmental factors such as rain, dust and weather erosion have led to a decrease in radium concentrations in these areas which fell within the permissible range of 33 Becquerel / kg. The concentrations of uranium in the samples under study ranged from 0.2622 ppm to 2.239 ppm, is higher than the natural limit of the background radiation (0.2 - 1.2) ppm, which indicates that radioactive pollution has entered the Iraqi environment. As well as, we find that the concentration of Radon The samples have risen by twenty times the normal limit in some samples, which indicates the danger of dealing with the polluted southern environment of Iraq.

Unperturbed inverse kinematics nucleon knockout measurements with a carbon beam

From superconductors to atomic nuclei, strongly-interacting many-body systems are ubiquitous in nature. Measuring the microscopic structure of such systems is a formidable challenge, often met by particle knockout scattering experiments. While such measurements are fundamental for mapping the structure of atomic nuclei, their interpretation is often challenged by quantum mechanical initial- and final-state interactions (ISI/FSI) of the incoming and scattered particles. Here we overcome this fundamental limitation by measuring the quasi-free scattering of 48 GeV/c 12C ions from hydrogen. The distribution of single protons is studied by detecting two protons at large angles in coincidence with an intact 11B nucleus. The 11B detection is shown to select the transparent part of the reaction and exclude the otherwise large ISI/FSI that would break the 11B apart. By further detecting residual 10B and 10Be nuclei, we also identified short-range correlated (SRC) nucleon-nucleon pairs, and provide direct experimental evidence for the separation of the pair wave-function from that of the residual many-body nuclear system. All measured reactions are well described by theoretical calculations that do not contain ISI/FSI distortions. Our results thus showcase a new ability to study the short-distance structure of short-lived radioactive atomic nuclei at the forthcoming FAIR and FRIB facilities. These studies will be pivotal for developing a ground-breaking microscopic understanding of the structure and properties of nuclei far from stability and the formation of visible matter in the universe.

The impact of (n,γ) reaction rate uncertainties of unstable isotopes on the i-process nucleosynthesis of the elements from Ba to W

ABSTRACT The abundances of neutron (n)-capture elements in the carbon-enhanced metal-poor (CEMP)-r/s stars agree with predictions of intermediate n-density nucleosynthesis, at Nn ∼ 1013–1015 cm−3, in rapidly accreting white dwarfs (RAWDs). We have performed Monte Carlo simulations of this intermediate-process (i-process) nucleosynthesis to determine the impact of (n,γ) reaction rate uncertainties of 164 unstable isotopes, from 131I to 189Hf, on the predicted abundances of 18 elements from Ba to W. The impact study is based on two representative one-zone models with constant values of Nn = 3.16 × 1014 and 3.16 × 1013 cm−3 and on a multizone model based on a realistic stellar evolution simulation of He-shell convection entraining H in a RAWD model with [Fe/H] = −2.6. For each of the selected elements, we have identified up to two (n,γ) reactions having the strongest correlations between their rate variations constrained by Hauser–Feshbach computations and the predicted abundances, with the Pearson product–moment correlation coefficients |rP| > 0.15. We find that the discrepancies between the predicted and observed abundances of Ba and Pr in the CEMP-i star CS 31062−050 are significantly diminished if the rate of 137Cs(n,γ)138Cs is reduced and the rates of 141Ba(n,γ)142Ba or 141La(n,γ)142La increased. The uncertainties of temperature-dependent β-decay rates of the same unstable isotopes have a negligible effect on the predicted abundances. One-zone Monte Carlo simulations can be used instead of computationally time-consuming multizone Monte Carlo simulations in reaction rate uncertainty studies if they use comparable values of Nn. We discuss the key challenges that RAWD simulations of i process for CEMP-i stars meet by contrasting them with recently published low-Z asymptotic giant branch (AGB) i process.

Neutral-current background induced by atmospheric neutrinos at large liquid-scintillator detectors. II. Methodology for in situ measurements

Future large liquid-scintillator (LS) detectors are competitive with and complementary to the water-Cherenkov detectors on the searches for diffuse supernova neutrino background and nucleon decay. In a companion paper, we have performed a systematic calculation of the neutral-current (NC) background induced by atmospheric neutrino interactions on $^{12}\mathrm{C}$ nuclei in LS detectors, which are expected to be crucially important for the experimental searches for the diffuse supernova neutrino background and nucleon decay. In this paper, we perform a systematic study on the measurement of the NC background and evaluate the associated uncertainties. We first exploit the characteristics of the NC background, in particular, the multiplicities of neutrons and pions, and the possible association with unstable residual nuclei. It turns out that the neutron multiplicity distribution is very powerful to discriminate among different models. Then, we develop a maximum-likelihood method to allow an in situ measurement of the NC interactions with a triple-coincidence signature. Finally, a data-driven approach is proposed to evaluate the uncertainty of the NC background in the search for the diffuse supernova neutrino background. We conclude that future large LS experiments like the Jiangmen Underground Neutrino Observatory will be able to make a unique contribution to the worldwide dataset to improve the prediction of atmospheric neutrino NC interactions on $^{12}\mathrm{C}$.

Study of the proton halo structure of nuclei 23Al and 27P using the binary cluster model

The neutron, proton, and matter densities of the ground state of the proton-rich 23Al and 27P exotic nuclei were analyzed using the binary cluster model (BCM). Two density parameterizations were used in BCM calculations namely; Gaussian (GS) and harmonic oscillator (HO) parameterizations. According to the calculated results, it found that the BCM gives a good description of the nuclear structure for above proton-rich exotic nuclei. The elastic form factors of the unstable 23Al and 27P exotic nuclei and those of their stable isotopes 27Al and 31P are studied by the plane-wave Born approximation. The main difference between the elastic form factors of unstable nuclei and their stable isotopes is caused by the variation in the proton density distributions, especially the details of the outer part. Moreover, the Glauber model is used to calculate the matter rms radii and reaction cross-section of these exotic nuclei. The calculated results of the mentioned nuclei give a good accordance with the experimental data.

Identifying Radio-active Galactic Nuclei among Radio-emitting Galaxies

Abstract Basing our analysis on ROGUE I, a catalog of over 32,000 radio sources associated with optical galaxies, we provide two diagnostics to select the galaxies where the radio emission is dominated by an active galactic nucleus (AGN), referred to in the paper as radio-AGNs. Each of these diagnostics can be applied independently. The first one, dubbed MIRAD, compares the flux F W3 in the W3 mid-infrared band of the Wide-field Infrared Survey Explorer telescope, with the radio flux at 1.4 GHz, F 1.4. MIRAD requires no optical spectra. The second diagnostic, dubbed DLM, compares the 4000 Å break strength, D n(4000), with the radio luminosity per unit stellar mass. The DLM diagram has already been used in the past, but not as stand-alone. For these two diagrams, we propose simple, empirical dividing lines that result in the same classification for the objects in common. These lines correctly classify as radio-AGN 99.5% of the extended radio sources in the ROGUE I catalog, and as star-forming galaxies 98%–99% of the galaxies identified as such by their emission-line ratios. Both diagrams clearly show that radio-AGNs are preferentially found among elliptical galaxies and among galaxies hosting the most massive black holes. Most of the radio sources classified as radio-AGNs in the MIRAD or DLM diagrams are either optically weak AGNs or retired galaxies.

129I and 247Cm in meteorites constrain the last astrophysical source of solar r-process elements.

The composition of the early Solar System can be inferred from meteorites. Many elements heavier than iron were formed by the rapid neutron capture process (r-process), but the astrophysical sources where this occurred remain poorly understood. We demonstrate that the near-identical half-lives [Formula: see text] of the radioactive r-process nuclei iodine-129 and curium-247 preserve their ratio, irrespective of the time between production and incorporation into the Solar System. We constrain the last r-process source by comparing the measured meteoritic ratio 129I/247Cm = 438 ± 184 with nucleosynthesis calculations based on neutron star merger and magneto-rotational supernova simulations. Moderately neutron-rich conditions, often found in merger disk ejecta simulations, are most consistent with the meteoritic value. Uncertain nuclear physics data limit our confidence in this conclusion.

Three-dimensional tracking multi-segmented proportional gas counter for [formula omitted]-decay spectroscopy of unstable nuclei

We report on the performance of a recently developed high-efficiency, low-background, three-dimensional tracking multi-segmented proportional gas counter (3DT-MSPGC), intended for β-decay spectroscopy of neutron-rich nuclei in the vicinity of neutron magic number N=126 at the KEK Isotope Separation System (KISS) facility. The 3DT-MSPGC uses two concentric cylindrical layers of proportional gas counters (16 per layer, 32 in total) featuring resistive anode wires (3 kΩ/cm). By independently measuring the charge deposition from both ends of each counter, we constrain β particle trajectories and determine where they intersect with the central axis of the 3DT-MSPGC. New compact charge-sensitive pre-amplifier modules, along with shaping amplifier and fast-timing amplifier modules, were developed to deduce the hit position by precisely measuring the charge deposition and timing. We have studied the performance of the 3DT-MSPGC in on- and off-line experiments. A longitudinal position resolution of ≤3.5 mm (FWHM) was achieved for each counter. The determination of the event trajectories allowed for suppression of background events, resulting in the background-event rate reaching 0.020(3) count-per-second (cps) while still maintaining a high-detection efficiency. This reduction of background is shown to improve the signal-to-noise ratio in determination of the half-life of 196Ir by a factor of 2.3(6), resulting in a significant improvement in achievable precision.