Nuclear Contribution Research Articles

Coulomb and nuclear excitations of Zn70 and Ni68 at intermediate energy

The reduced transition probabilities B(E2;0g.s.+→21+,22+) in Zn70 and the full B(E2;0g.s.+→2+) strength up to Sn=7.79MeV in Ni68 have been determined at the LISE/GANIL facility using the Coulomb-excitation technique at intermediate beam energy on a Pb208 target. The γ rays emitted in-flight were detected with an array of 46BaF2 crystals. The angles of the deflected nuclei were determined in order to disentangle and extract the Coulomb and nuclear contributions to the excitation of the 2+ states. The measured B(E2;0g.s.+→21+) of 1432(124) e2fm4 for Zn70 falls in the lower part of the published values which clustered either around 1600 or above 2000e2fm4, while the B(E2;0g.s.+→22+) of 53(7) e2fm4 agrees very well with the two published values. The relatively low B(E2;0g.s.+→21+) of 301(38) e2fm4 for Ni68 agrees with previous studies and confirms a local magicity at Z=28, N=40. Combining the results of the low-energy spectra of Ni68 and Zn70 and their shell-model interpretations, it is interesting to notice that four different shapes (spherical, oblate, prolate, and triaxial) are present. Finally, a summed E2 strength of only about 150e2fm4 has been found experimentally at high excitation energy, likely due to proton excitations across the Z=28 gap. The experimental distribution of this high-energy E2 excitation agrees with shell-model calculations, but its strength is about two times weaker.4 MoreReceived 19 May 2020Revised 8 April 2021Accepted 10 September 2021DOI:https://doi.org/10.1103/PhysRevC.104.034318©2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasElectromagnetic transitionsNuclear fragmentationNuclear structure & decaysProperties59 ≤ A ≤ 89Nuclear Physics

Nucleon momentum distribution of 56Fe from the axially deformed relativistic mean-field model with nucleon-nucleon correlations

Nucleon momentum distribution (NMD), particularly its high-momentum components, is essential for understanding the nucleon--nucleon ($ NN $) correlations in nuclei. Herein, we develop the studies of NMD of $^{56}\text{Fe}$ from the axially deformed relativistic mean-field (RMF) model. Moreover, we introduce the effects of $ NN $ correlation into the RMF model from phenomenological models based on deuteron and nuclear matter. For the region $ k<k_{\text{F}} $, the effects of deformation on the NMD of the RMF model are investigated using the total and single-particle NMDs. For the region $ k>k_{\text{F}} $, the high-momentum components of the RMF model are modified by the effects of $ NN $ correlation, which agree with the experimental data. Comparing the NMD of relativistic and non-relativistic mean-field models, the relativistic effects on nuclear structures in momentum space are analyzed. Finally, by analogizing the tensor correlations in deuteron and Jastrow-type correlations in nuclear matter, the behaviors and contributions of $ NN $ correlations in $^{56}\text{Fe}$ are further analyzed, which helps clarify the effects of the tensor force on the NMD of heavy nuclei.

Systematic study on the role of various higher-order processes in the breakup of weakly-bound projectiles

Abstract The virtual photon theory (VPT), which is based on first-order Coulomb dissociation restricted to the electric dipole (E1), has been successfully used to explain the breakup data for several cases. Our aim is to study the role of various higher-order processes that are ignored in the VPT, such as the nuclear breakup, interference between nuclear and Coulomb amplitudes, and multistep breakup processes mainly due to strong continuum-continuum couplings in the breakup of two-body projectiles on a heavy target at both intermediate and higher incident energies. For the purpose of numerical calculations, we employed eikonal version of three-body continuum-discretized coupled-channels (CDCC) reaction model. Our results for the breakup of 11Be and 17F on 208Pb target at 100, 250, and 520 MeV/A, show the importance of nuclear breakup contribution, and its significant role in the multistep processes. The multistep effect on Coulomb breakup for core-neutron projectile was found to be negligible, whereas it was important for core-proton projectile. Coulomb-nuclear interference (CNI) effect was also found to be non-negligible. Qantitatively, the multistep effects due to the nuclear breakup was found to depend on the incident energy through the energy dependence of the core-target and nucleon-target nuclear potentials. The nuclear breakup component, the CNI effect, and the multistep breakup processes are all found to be non-negligible; hence, the assumptions adopted in the VPT for the accurate description of breakup cross sections are not valid.

Nuclear energy contribution potential to secure electricity demand with low carbon emission and low risk of power plant in Indonesia

The Government of Indonesia has shifted the paradigm to envisage energy as capital to develop the country. By far, the electricity produced from the power plant, which reaches 283.8 TWh in 2018, mostly originated from coal-fired power plants (56.4%). The remains produced by gas power plant (20.2%), diesel (6.3%), and renewable energy (17.1%). In National Energy General Plan, it stated that the new and renewable energy should be utilized at least 23% by 2025 and 31% by 2050. The NRE potential which Indonesia has is around 431,745 MW. However, the installed capacity was only around 6,830 MW. Despite the large NRE potential, only a small portion of the capacity which already utilized for electricity production. In the 2014 National Energy Policy (KEN), the government-mandated five policy points regarding priority directions for national energy development, including nuclear as a last resort. Nuclear is one of the environmentally friendly energy sources and has considerable power potential, which can contribute 25% of total energy supply based on capacity factor and based load power plant approaches and synergy with other new and renewable energy resources for about 70% contribution from the total electricity supply. Nuclear energy has several features compared to other energy sources, including a cleaner and safer life cycle, high density energy as well as low cost for generating levelized cost and external cost. It is recommended that Indonesia consider nuclear energy as a potential new energy source to accelerate the country’s development.

Testing Quantum Electrodynamics with Exotic Atoms.

Precision study of few-electron, high-Z ions is a privileged field for probing high-field, bound-state quantum electrodynamics (BSQED). However, the accuracy of such tests is plagued by nuclear uncertainties, which are often larger than the BSQED effects under investigation. We propose an alternative method with exotic atoms and show that transitions may be found between circular Rydberg states where nuclear contributions are vanishing while BSQED effects remain large. When probed with newly available quantum sensing detectors, these systems offer gains in sensitivity of 1 to 2 orders of magnitude, while the mean electric field largely exceeds the Schwinger limit.

Towards spatially resolved magnetic small-angle scattering studies by polarized and polarization-analyzed neutron dark-field contrast imaging

In the past decade neutron dark-field contrast imaging has developed from a qualitative tool depicting microstructural inhomogeneities in bulk samples on a macroscopic scale of tens to hundreds of micrometers to a quantitative spatial resolved small-angle scattering instrument. While the direct macroscopic image resolution around tens of micrometers remains untouched microscopic structures have become assessable quantitatively from the nanometer to the micrometer range. Although it was found that magnetic structures provide remarkable contrast we could only recently introduce polarized neutron grating interferometric imaging. Here we present a polarized and polarization analyzed dark-field contrast method for spatially resolved small-angle scattering studies of magnetic microstructures. It is demonstrated how a polarization analyzer added to a polarized neutron grating interferometer does not disturb the interferometric measurements but allows to separate and measure spin-flip and non-spin-flip small-angle scattering and thus also the potential for a distinction of nuclear and different magnetic contributions in the analyzed small-angle scattering.

Polarized Neutron Diffraction in the Single-Crystal Studies

A review of various methods based on the use of polarized neutron diffraction with and without subsequent polarization analysis is presented. Various methods of polarized neutron diffraction for studying magnetic properties of materials have been theoretically substantiated. It is demonstrated that polarized neutrons can efficiently be used to determine the magnetic properties of structures, to separate magnetic and nuclear contributions, to analyze the magnetization-density distribution in crystals, and to study chiral effects. Examples of experimental studies, the results of which confirm the uniqueness of this technique for solving problems of physics of magnetic phenomena in solids, are presented.

New Thermonuclear Reaction Rate Equations for Radiative Neutron Capture

The radiative neutron capture reaction rates have been studied at very low energies which are of interest for nuclear astrophysics. The rates for many of these reactions have remained independent of temperature so far. The temperature dependence of the thermonuclear reaction rates have been explored within the statistical model. Apart from the compound nuclear contribution, the pre-equilibrium as well as the direct effects have been taken into account. The corresponding Maxwellian-averaged thermonuclear reaction rates of relevance in astrophysical plasmas at temperatures in the range from 10$^6$ K to 10$^{10}$ K have been calculated. Analytical expression as a function of $T_9$ has been provided for $^6$Li(n,$\gamma$)$^7$Li by fitting the calculated reaction rate.

UNDI: An open-source library to simulate muon-nuclear interactions in solids

We present UNDI, an open-source program to analyze the time dependent spin polarization of an isolated muon interacting with the surrounding nuclear magnetic dipoles in the context of standard muon spin rotation and relaxation spectroscopy experiments.The code can perform both exact and approximated estimates of the muon polarization function in presence of external fields and electric field gradients on the nuclei surrounding the muon.We show that this tool, combined to ab initio estimations of the electric field gradient at the nuclei interacting with the muon, can become a valuable complement to supercell based identifications of muon sites in crystals when large nuclear magnetic moments are present in the sample. In addition, it allows to properly investigate physical properties influenced by the presence of a non-negligible electric field gradient such as avoided level crossing resonance, nature of the ground state, disentanglement of electronic and nuclear magnetic moments or charge ordered states.The efficiency and effectiveness of this method is shown along the lines of three realistic examples. Program summaryProgram Title: UNDICPC Library link to program files:http://dx.doi.org/10.17632/grp8njy6gz.1Developer’s repository link:https://github.com/bonfus/undiCode Ocean capsule:https://codeocean.com/capsule/8365303Licensing provisions: GPLv3Programming language: PythonNature of problem: To simplify and potentially automate the analysis of the nuclear contribution to muon polarization functions in crystalline materials.Solution method: A python library that provides a set of tools to efficiently solve the spin Hamiltonian describing the interaction between the muon and its neighboring nuclei. The code provides the time development of the spin polarization of the muon subject to external fields and accounts for quadrupolar interactions at the nuclear sites. The solution is sought at quantum level accuracy and Hilbert spaces with dimension up to one million can be handled, thus providing accurate results for all standard experimental conditions.

Specific Heat of Holmium in Gold and Silver at Low Temperatures

The specific heat of dilute alloys of holmium in gold and in silver plays a major role in the optimization of low temperature microcalorimeters with enclosed ^{163}{{text {Ho}}}, such as the ones developed for the neutrino mass experiment ECHo. We investigate alloys with atomic concentrations of x_{{{text {Ho}}}}=0.01{-}4% at temperatures between 10 and 800,{{{hbox {mK}}}}. Due to the large total angular momentum J=8 and nuclear spin I=7/2 of {{text {Ho}}}^{3+} ions, the specific heat of Au:Ho and Ag:Ho depends on the detailed interplay of various interactions, including contributions from the localized 4f electrons and nuclear contributions via hyperfine splitting. This makes it difficult to accurately determine the specific heat of these materials numerically. Instead, we measure their specific heat by using three experimental setups optimized for different concentration and temperature ranges. The results from measurements on six holmium alloys demonstrate that the specific heat of these materials is dominated by a large Schottky anomaly with its maximum at Tapprox 250,{{{hbox {mK}}}}, which we attribute to hyperfine splitting and crystal field interactions. RKKY and dipole–dipole interactions between the holmium atoms cause additional, concentration-dependent effects. With regard to ECHo, we conclude that for typical operating temperatures of Tle 20,{{{hbox {mK}}}}, silver holmium alloys with x_{{{text {Ho}}}}gtrsim 1% are suited best.

Astrophysical production of 146Sm in nuclear p - processes

The large time of life of 146Sm suggests the possibility to use this p - nuclide as astrophysical chronometer to study the geochemical galactic evolution. Due to the high temperature and large densities of gamma quanta, neutrons and protons in stellar environment 146Sm nucleus can be obtained in (γ,n), (n,2n), (p,2n) processes on 147Sm.The knowledge of corresponding cross sections of gamma rays, neutrons and alpha induced processes is of a great importance for the explanation of (146Sm/144Sm) ratio uncertainties observed on the Earth, meteorites, Moon and other celestial bodies.Cross sections of (γ,n), (n,2n), (α,γ) processes induced by fast gamma rays, neutrons and alphas on 147Sm and 142Nd, from threshold up to 25 MeV were evaluated and predicted in the frame of Hauser-Feshbach statistical model by using Talys software and the own computer programs. For each nuclear reaction contribution of direct, compound and pre-equilibrium mechanisms were determined. Theoretical evaluations are compared with existing experimental data. Parameters of optical potential in the incident and emergent channels and of nuclear densities were extracted. Calculated cross sections together with corresponding nuclear data were used in the evaluation of astrophysical rates necessary in the determination of elemental abundances as needed by nuclear astrophysical networks.

Nuclear magnetization distribution effect in molecules: Ra+ and RaF hyperfine structure.

Recently, the first laser spectroscopy measurement of the radioactive RaF molecule has been reported by Ruiz et al. [Nature 581, 396 (2020)]. This and similar molecules are considered to search for the new physics effects. The radium nucleus is of interest as it is octupole-deformed and has close levels of opposite parity. The preparation of such experiments can be simplified if there are reliable theoretical predictions. It is shown that the accurate prediction of the hyperfine structure of the RaF molecule requires to take into account the finite magnetization distribution inside the radium nucleus. For atoms, this effect is known as the Bohr-Weisskopf (BW) effect. Its magnitude depends on the model of the nuclear magnetization distribution which is usually not well known. We show that it is possible to express the nuclear magnetization distribution contribution to the hyperfine structure constant in terms of one magnetization distribution dependent parameter: BW matrix element for 1s-state of the corresponding hydrogen-like ion. This parameter can be extracted from the accurate experimental and theoretical electronic structure data for an ion, atom, or molecule without the explicit treatment of any nuclear magnetization distribution model. This approach can be applied to predict the hyperfine structure of atoms and molecules and allows one to separate the nuclear and electronic correlation problems. It is employed to calculate the finite nuclear magnetization distribution contribution to the hyperfine structure of the 225Ra+ cation and 225RaF molecule. For the ground state of the 225RaF molecule, this contribution achieves 4%.

Half-lives of proton emitters studied with the KDE0v1 Skyrme interaction

The half-lives of proton radioactivity of proton emitters are investigated theoretically by using KDE0v1 Skyrme interaction. The total barrier potential in the proton radioactive nuclei is calculated as the sum of the nuclear, Coulomb and centrifugal contributions. The Hartree-Fock nuclear density distributions is used in calculating the nuclear as well as the Coulomb interaction potentials. The quantum mechanical tunneling probability is calculated within the WKB approximation. These calculations provide reasonable estimates for the observed proton radioactivity lifetimes.

Muon Spectroscopy for Investigating Diffusion in Energy Storage Materials

We review recent applications of positive muon spin relaxation (μSR) spectroscopy as an active probe of ion diffusion in energy storage materials. μSR spectroscopy allows the study of ionic diffusion in solid-state materials on a time scale between 10−5 and 10−8 s where most long-range and consecutive short-range jumps of ions between interstitial sites occur. μSR also allows one to probe and model ionic diffusion in materials that contain magnetic ions, since both electronic and nuclear contributions to the muon depolarization can be separated, making μSR an excellent technique for the microscopic study of the ionic motions in crystalline materials. We highlight a series of battery materials for which μSR has provided insight into intrinsic ionic conduction and magnetic properties without interference of external factors, such as the presence of magnetic ions, macroscopic particle morphologies, or elaborate measurement setups.

Assessment of the French nuclear energy system – A case study

The country with the highest nuclear power contribution to its energy matrix is France with 72.28%. The French nuclear history reveals that they trust in reprocessing option since an early stage of the nuclear power plants. Therefore, this work is devoted to studying the two options of a fuel cycle, i.e., Open Fuel Cycle (OFC) and Closed Fuel Cycle (CFC) for this country and the economics of each scenario. The assessment begins using the MESSAGE, since the first official registration by the International Atomic Energy Agency (IAEA), which is in 1970 and tries to follow the model until 2016. After that, the MESSAGE adjusts the energy planning to fit best until 2034 remaining the nuclear activity in this country. The results show the best reactor option to supply 50000 MWyr until 2034 using the two fuel cycle models. Finally, it is shown the amount of resources needed to maintain the nuclear power industry in France and justify the French option of the fuel cycle based on the economic results. The results show the use of nuclear resources taking advantage of a closed fuel cycle. The idea is to show the sustainability of a closed fuel cycle, applying this methodology to countries in nuclear development with a different scenario.

Calculation of the electronic, nuclear, rotational, and vibrational stopping cross sections for H atoms irradiation on H2, N2 and O2 gas targets at low collision energies

In this work, we present a study of hydrogen atoms interacting with hydrogen, nitrogen, and oxygen molecules in the gas phase in order to determine the projectile energy loss, the stopping cross section, and energy deposition with implication in hydrogen and proton dosimetry and radiotherapy. Our calculations are performed with a density-functional tight-binding (DFTB) as well as by an ab initio electron-nuclear dynamic (END). The H atoms have a low collision energy in the range of 1–100 eV for the DFTB and 1–1000 eV for the END. We decompose the projectile energy deposition into its electronic, nuclear, rotational, and vibrational energy target contributions. We find that for low collisions energy, DFTB and END are in fair agreement when comparing the nuclear and rotational contributions. However, we find discrepancies for the vibrational and electronic energy loss between both approaches. The largest discrepancy is found in the electronic energy loss as DFTB carries the electronic dynamics in the ground state. We confirm that the electronic stopping cross section is proportional to the projectile velocity as obtained by END showing a threshold effect and that it is underestimated by codes like SRIM. Our study shows that at low collision energies a quantum-classical molecular dynamics approach as DFTB can be used to determine the energy-loss process of a projectile penetrating a material target. Finally, we compare our results to available experimental data finding good agreement when extrapolated to high collision energies.

The puzzling taxonomic rank of Pijnackeria hispanica, a chimerical hybrid androgen (Insecta, Phasmida)

The stick-insect genus Pijnackeria includes four diploid bisexual and two polyploid (3n, 4n) parthenogenetic species. Earlier analyses of the tetraploid parthenogen P. hispanica using mitochondrial markers allowed tracing its maternal ancestry to Pijnackeria originis, while no maternal nuclear contribution was found, thus suggesting an androgenetic and hybrid origin. The recently described Pijnackeria recondita—showing, among other features, a specific antennal structure linking it to the tetraploid parthenogen—prompted us to check whether the new species could be the unknown paternal ancestor of P. hispanica. In this work, we use karyology and molecular analysis of the mitochondrial gene cytochrome c oxidase subunit 2 (cox2) and the nuclear gene elongation factor 1 subunit α (ef1-α) to investigate the origin of such a complex tetraploid hybrid parthenogen. The molecular analysis supported P. recondita as being a paternal ancestor of P. hispanica, but also suggested that two more fathering species have to be taken into account: P. barbarae and the unknown paternal ancestor of the triploid hybrid P. masettii. Therefore, P. hispanica is apparently a polyphyletic chimeric androgen, which we propose to indicate as an androgenetic complex. Our data also revealed that P. hispanica is between 1.96 Myr and 3.31 Myr old, making it the oldest parthenogenetic taxon discovered among insects.

Hard-X-ray-selected active galactic nuclei – I. A radio view at high frequencies

ABSTRACT A thorough study of radio emission in active galactic nuclei (AGNs) is of fundamental importance to understand the physical mechanisms responsible for the emission and the interplay between accretion and ejection processes. High-frequency radio observations can target the nuclear contribution of smaller emitting regions and are less affected by absorption. We present JVLA 22 and 45 GHz observations of 16 nearby (0.003 ≤ z ≤ 0.3) hard-X-ray-selected AGNs at the (sub)-kpc scale with tens μJy beam−1 sensitivity. We detected 15/16 sources, with flux densities ranging from hundreds μJy to tens Jy (specific luminosities from ∼1020 to ${\sim}10^{25}\, \mathrm{ W}\, \mathrm{ Hz}^{-1}$ at 22 GHz). All detected sources host a compact core, with eight being core-dominated at either frequencies, the others exhibiting also extended structures. Spectral indices range from steep to flat/inverted. We interpret this evidence as either due to a core+jet system (6/15), a core accompanied by surrounding star formation (1/15), to a jet oriented close to the line of sight (3/15), to emission from a corona or the base of a jet (1/15), although there might be degeneracies between different processes. Four sources require more data to shed light on their nature. We conclude that, at these frequencies, extended, optically thin components are present together with the flat-spectrum core. The LR/LX ∼ 10−5 relation is roughly followed, indicating a possible contribution to radio emission from a hot corona. A weakly significant correlation between radio core (22 and 45 GHz) and X-ray luminosities is discussed in the light of an accretion–ejection framework.

Nuclear and magnetic small-angle neutron scattering in self-organizing nanostructured Fe1−xCrx alloys

Small-angle neutron scattering (SANS) in self-organizing nanostructured Fe1-xCrx (x = 0.21, 0.43 and 0.53) alloys has been studied. The relation between the nuclear and magnetic contributions depends on the alloy composition and the extent of self-organizing due to the demixing of Fe and Cr. When the demixing is pronounced with a large concentration fluctuation amplitude, the two scattering contributions are very similar, whereas when the concentration fluctuation amplitude is very small, the magnetic contribution is negligible compared to the nuclear contribution. The relation between the scattering signals is critical when assessing the demixing in Fe1-xCrx alloys by SANS, which has been mostly ignored in prior works in the literature.

Exploiting Radioactive Isotopes: from Pollutant Tracking to Solid State Studies Using a Combined Ab Initio and PAC Approach

In this review we present examples of using radioactive isotopes as probes to study functional materials of fundamental and applied interest presenting colossal magnetoresistance, multiferroic effects, and magnetostructural coupling. Most of the works exploit the hyperfine properties, Electric Field Gradient (EFG) and Hyperfine Magnetic Field (HMF), of these probes through Perturbed Angular Correlation (PAC) spectroscopy. The measurements were complemented with density functional theory calculations to model the relevant properties and correlate the EFG with the electric polarization. We also present a methodological and nuclear physics related contribution consisting on the characterization of a new short‐lived isotope adequate for PAC studies. Finally, an ultra‐sensitive method to quantify the uptake of Hg by nano sorbents based on the tracking the radioactive isotopes of mercury is also reviewed. These works showcase the diversity of our research with radioisotopes, at the interface of different science fields, with combination of different methodologies and different motivations such as fundamental materials physics and chemistry or environmental concerns.