Atomic Nuclei Research Articles

Contribution of neutron diffraction to the study of crystallo-solvates (molecular compounds) from polymers and from supramolecular polymers

This paper presents a short outlook of the potentiality of neutron diffraction for the structural study of crystallo-solvates (molecular compounds) prepared from polymer and supramolecular with appropriate solvents. As neutrons interact only with the atom nucleus, neutronic contrast can be varied by using isotopes. The difference between the scattering lengths of hydrogen and deuterium is suitable in the case of polymers and/or supramolecular polymers that both contain a large number of hydrogen atoms, especially when it comes to studying the molecular compounds they form with solvents. By toying with the isotopic labelling of each species, one may access up to four different diffraction patterns, something not attainable by X-ray diffraction. Here, diffraction investigations of molecular compounds from poly ethylene oxide, syndiotactic polystyrene, and a supramolecular polymer prepared from a tri arylamine trisamide are presented. The complementary of neutron with X-rays is shown and discussed.

First Results of Studying EAS Cores Using a High-Mountain Ionization Calorimeter

In high-altitude experiments to study the central cores of EAS at E0 ≳ 1016 eV (√s ≳ 5 TeV) using X-ray emulsion chambers and ionization calorimeters, phenomena such as the coplanarity of the arrival of the most energetic particles in super families of γ-rays and hadrons and a so-called Tien Shan effect (too slow absorption of cascades initiated by high-energy hadrons in the calorimeter) were observed. These effects could not be reproduced within the framework of theoretical models of the 80s and 90s. The coplanarity is explained via a process of coplanar generation of the most energetic secondary particles in interactions of super high-energy hadrons with nuclei of air atoms. Perhaps the Tien Shan effect could be explained using a high cross section for the generation of fragmentation-region charmed hadrons. To study these phenomena, a new set of detectors has been developed, including the world’s highest high-mountain ionization calorimeter, “Hadron-55”. This paper presents the initial experimental results.

Secondary fragments of proton and helium ion beams in High-Density Polyethylene phantom: A Monte Carlo simulation study

In hadrontherapy, secondary fragments are generated by nuclear interactions of the incident heavy ion beam with the atomic nuclei of the target. It is important to determine the yield of production and the dose contribution of these secondary fragments in order to determine the radiobiological effectiveness more accurately. This work aims to fully identify the secondary fragments generated by nuclear interactions of proton and helium (4He) ion beams in a High-Density Polyethylene (HDPE) target and to investigate the dose contributions by secondary fragments. Incident protons with energies of 55.90 MeV and 105.20 MeV and helium ions with energies of 52.55 MeV/u and 103.50 MeV/u in the HDPE phantom have been investigated by the means of Geant4 Monte Carlo (MC) simulations. Simulated results were validated using NASA Space Radiation Laboratory (NSRL) Bragg curves experimental data. The results showed that the dose contribution of secondary fragments deriving from helium ion beams is three times higher than in the case of proton beams. This is due to a higher production of nuclear fragments in the case of helium ion beams. This work contributes to a better understanding of secondary fragments generated by protons and helium ions in the HDPE target.

Структура и надмолекулярное упорядочение L- и D-аспарагината хитозана

Chitosan (CS) with a viscosity-average molecular weight of 200 kDa and a deacetylation degree of 82 mol%, produced by Bioprogress Ltd. (RF) has been used in this work. Aqueous solutions of enantiomeric salt complexes of CS with L- and D-aspartic acid (AspA) have been obtained at an equimolar CS:AspA ratio, in terms of amino groups. Powders of CS·L-(D-) AspA salts have been isolated from the corresponding solutions by evaporation of water and stored in a desiccator at zero humidity. It has been established that under such conditions a water-soluble salt form of the polymer with lamellar light beige particles 0.05–1.0 mm in size is formed. Using the methods of elemental analysis, IR and NMR spectroscopy, and X-ray diffractometry, the chemical interaction of CS with L-(D-)AspA in aqueous solution and condensed state has been evaluated, and the chemical structure and supramolecular ordering of these enantiomeric salts have been studied. It has been established that, according to the classification of K. Ogawa et al., the formula unit CS·L-(D-)AspA corresponds to non-hydrated salts of type I, in which water molecules are replaced by acid anions. IR spectroscopy confirmed the donor--acceptor polymer–acid interaction and revealed a developed system of intermolecular and intramolecular contacts. One- and two-dimensional NMR spectroscopy showed the interaction of pairs of atomic nuclei between H3–H6 of the polymer and 2Hβ or Hα of the acid, H1 or H2 and Hα, H1 and H3–H6, due to the spatial proximity of protons in repeating monomer units, in the “bend” chain segments removed along the chain, and in neighboring macromolecules. For CS·L-AspA, additional resonances have been identified between H2 and H3–H6 of the polymer, for CS·D-AspA these have been between H1 or H 2. X-ray diffractometry has revealed a highly ordered orientation of macrochains and a high crystallinity degree, untypical for CS salts. The salt complex CS·D-AspA, in contrast to CS·L-AspA, is characterized by a smaller amount of crystallization water, a more ordered supramolecular structure, and a more developed system of intermolecular and intramolecular contacts.

About elementary particles

It is shown that only stable particles can be elementary particles. The fundamental elementary particles are positive, negative and neutral particles of space. Photons and neutrinos are formed from them, which are elementary particles of electrons, positrons and protons. A neutral photon consists of a positive elementary particle of space, around which a negative elementary particle of space rotates. A neutrino consists of a negative elementary particle of space, around which a positive elementary particle of space rotates. An electron has a structure consisting of negative and neutral photons connected by negative elementary particles of space. The positron has a structure consisting of positive and neutral photons connected by negative elementary particles of space. A proton consists of a positively charged nucleus around which electrons rotate. The proton nucleus consists of positrons bound by neutrino particles. Atomic nuclei consist of positive and neutral protons connected by the exchange of electrons and neutrino particles. The carriers of electromagnetic interaction are positive and negative elementary particles of space. The carriers of the gravitational interaction are neutral elementary particles of space. Electromagnetic, gravitational and inertial forces are the forces of space. Space is an equilibrium system, just like the whole universe.

В.И. Вернадский и новая парадигма

The main directions of V.I.Vernadsky's scientific activity during the period of the scientific revolution occurred at the end of the 19th and until the middle of the20th centuries are briefly listed. His decisive contribution to the initial research and practical application of the phenomenon of radioactivity and nuclear physics is shown. Based on the discovery of low-energy nuclear reactions more than 30 years ago, the development of Vernadsky's ideas about the role of radioactivity − the transformation of some chemical elements into other chemical elements − in geology, in the thermal balance of the Earth, in the prevalence of trace chemical elements is presented. Main provisions of the theory of low-energy nuclear reactions in condensed matter are listed: the threshold for excitation of the medium is indicated; shown is the possibility of generating a strong magnetic field in a unidirectional flow of electrons in a quasineutral plasma with the pairing of free electrons, and, subsequently, the pairing of atomic electrons into orthobosons with the latter forming a Bose-Einstein condensate, in which a new state of matter is formed − transatoms, which are combined, due to their ultra-strong magnetic fields, into nuclear transmolecule, in which multinuclear transmutation reactions occur with non-radioactive products; with the transformation of transmolecules into different sets of stable nuclei, subject to all conservation laws. In this case, the collective parameter that characterizes the quasi-equilibrium distribution of the mass numbers of isotopes – reaction products – is the “thermodynamic” coefficient of the energy content of the medium. Natural nucleosynthesis in the era of recombination of the Universe, which gave rise to the formation and development of organic chemical, and subsequently biochemical synthesis, is described. The development of Vernadsky's doctrine of the biosphere and noosphere of the Earth is supplemented by the concept of fractality of material, including biological structures with the further evolution of living matter, as well as by the concept of planetary nucleosynthesis. Starting from the idea of planetary nucleosynthesis, based on the mechanism of multinuclear quantum transitions of some atomic nuclei to others, a new doctrine of the geological development of the Earth and the foundations of quantum planetology were formulated, which explained the strict temporal cyclicity observed in the geological activity of the Earth associated with galactic jet energy flows. The issues discussed may become a basis for those directions in scientific research that will form a new paradigm, a new worldview.

Colliding heavy nuclei take multiple identities on the path to fusion

The properties of superheavy elements probe extremes of physics and chemistry. They are synthesised at accelerator laboratories using nuclear fusion, where two atomic nuclei collide, stick together (capture), then with low probability evolve to a compact superheavy nucleus. The fundamental microscopic mechanisms controlling fusion are not fully understood, limiting predictive capability. Even capture, considered to be the simplest stage of fusion, is not matched by models. Here we show that collisions of 40Ca with 208Pb, experience an ‘explosion’ of mass and charge transfers between the nuclei before capture, with unexpectedly high probability and complexity. Ninety different partitions of the protons and neutrons between the projectile-like and target-like nuclei are observed. Since each is expected to have a different probability of fusion, the early stages of collisions may be crucial in superheavy element synthesis. Our interpretation challenges the current view of fusion, explains both the successes and failures of current capture models, and provides a framework for improved models.

Development and evaluation of boron carbide-modified unsaturated polyester resin for use as neutron radiation Protection

Neutrons are electrically neutral particles that can penetrate through various materials and interact with atomic nuclei. Neutrons can emit radiation with varying degrees of energy, which can be harmful to both living organisms and the environment. The objective of this study is to evaluate the thermal neutron (0.025 eV) shielding properties of unsaturated polyester resin with boron carbide content ranging from 0 to 20 wt% for use as neutron shielding materials. The FLUKA Monte Carlo simulation was utilized to evaluate the interactions between thermal neutrons and materials with a thickness of 5 cm. The total cross-section, mean free path, and half-value thickness were calculated to assess the shielding properties of materials. The results indicated that as the boron carbide content increased, the total cross-section increased while the mean free path and half-value thickness decreased. In addition, the polyester resin with 20 wt% of boron carbide exhibited the best properties for shielding thermal neutrons. Thus, this study suggests that unsaturated polyester resin containing boron carbide can be used as an effective material for shielding thermal neutrons.

Development of a semi-cylindrical time projection chamber prototype for (3He,t\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{3}{\ extrm{He}},t$$\\end{document}) charge exchange reaction experiment

The charge exchange (CE) reaction is an effective probe to study the structure of atomic nuclei in the isospin dimension, which has been studied for decades. To expand the range of nuclei studied by CE reactions to a wider range and research the structure characteristics of unstable nuclei, including the isospin symmetry, spin-isospin excitation, and nuclear symmetry energy, a semi-cylindrical time projection chamber (scTPC) prototype was designed and constructed to probe (3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{\ extrm{3}}$$\\end{document}He,t) CE reactions in inverse kinematics. The 266 nm UV laser was used to achieve electron-drift-velocity calibration. The scTPC has an energy resolution (FWHM) of 5.6% for α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document} particles emitted by 241\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{\ extrm{241}}$$\\end{document}Am radioactive source. The position resolution of scTPC is described by the residual method. The spatial resolution on the pad plane is 409 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upmu $$\\end{document}m. And the position resolution in the drift direction is 326 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upmu $$\\end{document}m, equivalent to an angular resolution of 0.4∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ $$\\end{document}. These performances suggest that the scTPC can measure ΔE\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta E $$\\end{document}and particle tracks precisely. The successful development of the scTPC prototype provides better conditions for the next step of experimental data analysis and processing.

Moment of Inertia and Dynamical Symmetry

We investigate how the moment of inertia of the atomic nucleus can be calculated in terms of the invariant operator of its SU(3) symmetry. This question is important for model Hamiltonians containing the moment of inertia explicitly, e.g., those with multichannel dynamical symmetry, which describes many different bands in a unified way.

INVESTIGATION OF THE EFFECT OF SMALL THERMAL NEUTRON FLUXES ON THE PROPERTIES OF BACTERIA RHIZOBIUM PHASEOLI IS TAAS-80 TJ AND BACILLUS MEGATERIUM VAR. PHOSPHATICUM

In this work, the effects of a small thermal neutron flux on the growth rate of Rhizobium phaseoli IS TAAS-80 TJ and Bacillus megaterium var. phosphaticum bacteria intended for use in the production of micronutrients were studied. The phenomenon of germination of grow rate of bacteria under irradiation with small fluxes of thermal neutrons has been discovered. The best result was obtained with thermal neutron fluxes of 5.4-106 Fluence, at which the grow rate of bacteria increases by 5-6 times. It has been experimentally shown that one of the possible mechanisms of the influence of thermal neutrons on the properties of biological objects is the interaction of thermal neutrons by the nuclei of light atoms of the composition of these objects. For this purpose, the IR spectra of the bacteria Rhizobium phaseoli IS TAAS-80 TJ and Bacillus megaterium var. phosphaticum were studied and the effect of a small thermal neutron flux on the spectral characteristics of these bacteria was estimated. It was found that in some bands of the IR spectrum of bacteria, when they are irradiated with small fluxes of thermal neutrons, the optical density intensity ratio changes. The greatest change is observed with thermal neutron fluxes of 5.4-106 Fluence, which correlates with an increase in the growth rate of bacteria by 5-6 times. It has been established that the change in the biological activity of bacteria is associated with a change in methyl groups. It has been experimentally shown that one of the possible mechanisms of the influence of thermal neutrons on the IR spectrum of the bacteria Rhizobium phaseoli IS TAAS-80 TJ and Bacillus megaterium var. phosphaticum is a nuclear reaction of radiation capture of thermal neutrons by nuclei of nitrogen atoms of the species . It is assumed that the mechanism of changing the activity of bacteria under the influence of thermal neutrons is due to a change in the conformation of DNA chains at certain sites and methylation of DNA, proteins and polymerase.

Applications of different machine learning methods on nuclear charge radius estimations

Theoretical models come into play when the radius of nuclear charge, one of the most fundamental properties of atomic nuclei, cannot be measured using different experimental techniques. As an alternative to these models, machine learning (ML) can be considered as a different approach. In this study, ML techniques were performed using the experimental charge radius of 933 atomic nuclei (A ≥ 40 and Z ≥ 20) available in the literature. In the calculations in which eight different approaches were discussed, the obtained outcomes were compared with the experimental data, and the success of each ML approach in estimating the charge radius was revealed. As a result of the study, it was seen that the Cubist model approach was more successful than the others. It has also been observed that ML methods do not miss the different behavior in the magic numbers region.

Recent development and prospect on heavy-ion collisions in colliders

Heavy ion collisions play a key role in advancing our understanding of the universe. These are collisions in which two atomic nuclei collide at high energy, releasing large amounts of energy and creating new elements. One of the fundamental theories of heavy-ion collisions is the quark-gluon plasma (QGP) theory. It suggests that in collisions at sufficiently high energies, the quarks and gluons of the colliding nuclei are no longer confined to individual particles, but form a new state of matter. In some heavy-ion collisions, the QGP may exhibit properties similar to those found in the early universe. In addition, studying heavy ion collisions could help answer some fundamental questions, such as the origin of mass and the nature of dark matter. This article focuses on the experimental setups related to Heavy-ion collisions and the results obtained by the researchers so far. The focus is on the more cutting-edge research built on Relativistic Heavy-ion Colliders. This article provides a partial summary of these results and an outlook on their future development.

Determination of the Neutron Skin of ^{208}Pb from Ultrarelativistic Nuclear Collisions.

Emergent bulk properties of matter governed by the strong nuclear force give rise to physical phenomena across vastly different scales, ranging from the shape of atomic nuclei to the masses and radii of neutron stars. They can be accessed on Earth by measuring the spatial extent of the outer skin made of neutrons that characterizes the surface of heavy nuclei. The isotope ^{208}Pb, owing to its simple structure and neutron excess, has been in this context the target of many dedicated efforts. Here, we determine the neutron skin from measurements of particle distributions and their collective flow in ^{208}Pb+^{208}Pb collisions at ultrarelativistic energy performed at the Large Hadron Collider, which are mediated by interactions of gluons and thus sensitive to the overall size of the colliding ^{208}Pb ions. By means of state-of-the-art global analysis tools within the hydrodynamic model of heavy-ion collisions, we infer a neutron skin Δr_{np}=0.217±0.058 fm, consistent with nuclear theory predictions, and competitive in accuracy with a recent determination from parity-violating asymmetries in polarized electron scattering. We establish thus a new experimental method to systematically measure neutron distributions in the ground state of atomic nuclei.

Impact of nuclear rotation corrections on alpha decay half-lives of superheavy nuclei within 98 ≤ Z ≤ 120

The influence of nuclear rotation on the decay half-lives of superheavy nuclei within the range 98≤Z≤120 is investigated using the axially deformed relativistic Hartree-Bogoliubov theory in the continuum (DRHBc) with the PC-PK1 parameter set. The deduced DRHBc decay energies (with and without the rotation effect) are compared with those calculated from the macroscopic-microscopic WS4 and the available experimental binding energies. Six semi-empirical formulae, such as the Viola-Seaborg formula (VSS), the modified Brown formula (mB1), the semi-empirical relationship based on fission theory (SemFIS2), the Royer formula (R), the Wang formula (Wang) and the modified YQZR formula (MYQZR) are employed to estimate the half-lives of α decay. Among these formulae, the half-live predictions of SemFIS2 are found to gradually deviate from the systematic trend beyond Nd=184, showing that the probability of undergoing spontaneous fission is less feasible beyond this point. A minimum is observed at Nd=184, reflecting its neutron shell closure for the mass region considered on the nuclear chart. The results further indicate that, for 98≤Z≤104, the predictions of all semi-empirical formulae are more closely matched to the available experimental data when the rotation effect is taken into account. However, we have demonstrated that the effect of nuclear rotation gradually reduces as the atomic nucleus becomes heavier.

Exploration of origin and breaking mechanism of pseudospin symmetry in relativistic point-coupling model with similarity renormalization group

The pseudospin symmetry (PSS) is an important physical concept in atomic nuclei. The relativistic point-coupling model is first used to explore the origin and breaking mechanism of PSS in real nuclei with 208Pb as an illustrated example. PSS observed in the single particle spectra of heavy nuclei is reproduced in the present calculation. The influences of the different point-coupling interactions on PSS are investigated, it is found that the four-fermion scalar and vector couplings play a dominate role at PSS. The quality of PSS depends on the competition of four-fermion scalar and vector couplings. Those the PSS is better for the weakly bound levels and the energy splittings are more sensitive to the interaction strengths for the deeply bound levels are well explained in terms of the derivative of Σ potential with r. In combination with the similarity renormalization group, the origin and breaking mechanism of PSS are clarified.

Neutron crystallographic refinement with REFMAC5 from the CCP4 suite.

Hydrogen (H) atoms are abundant in macromolecules and often play critical roles in enzyme catalysis, ligand-recognition processes and protein-protein interactions. However, their direct visualization by diffraction techniques is challenging. Macromolecular X-ray crystallography affords the localization of only the most ordered H atoms at (sub-)atomic resolution (around 1.2 Å or higher). However, many H atoms of biochemical significance remain undetectable by this method. In contrast, neutron diffraction methods enable the visualization of most H atoms, typically in the form of deuterium (2H) atoms, at much more common resolution values (better than 2.5 Å). Thus, neutron crystallography, although technically demanding, is often the method of choice when direct information on protonation states is sought. REFMAC5 from the Collaborative Computational Project No. 4 (CCP4) is a program for the refinement of macromolecular models against X-ray crystallographic and cryo-EM data. This contribution describes its extension to include the refinement of structural models obtained from neutron crystallographic data. Stereochemical restraints with accurate bond distances between H atoms and their parent atom nuclei are now part of the CCP4 Monomer Library, the source of prior chemical information used in the refinement. One new feature for neutron data analysis in REFMAC5 is refinement of the protium/deuterium (1H/2H) fraction. This parameter describes the relative 1H/2H contribution to neutron scattering for hydrogenisotopes. The newly developed REFMAC5 algorithms were tested by performing the (re-)refinement of several entries available in the PDB and of one novel structure (FutA) using either (i) neutron data only or (ii) neutron data supplemented by external restraints to a reference X-ray crystallographic structure. Re-refinement with REFMAC5 afforded models characterized by R-factor values that are consistent with, and in some cases better than, the originally deposited values. The use of external reference structure restraints during refinement has been observed to be a valuable strategy, especially for structures at medium-low resolution.

Strong Evidence for ^{9}N and the Limits of Existence of Atomic Nuclei.

The boundaries of the chart of nuclides contain exotic isotopes that possess extreme proton-to-neutron asymmetries. Here we report on strong evidence of ^{9}N, one of the most exotic proton-rich isotopes where more than one half of its constitute nucleons are unbound. With seven protons and two neutrons, this extremely proton-rich system would represent the first-known example of a ground-state five-proton emitter. The invariant-mass spectrum of its decay products can be fit with two peaks whose energies are consistent with the theoretical predictions of an open-quantum-system approach; however, we cannot rule out the possibility that only a single resonancelike peak is present in the spectrum.

Quantum entanglement patterns in the structure of atomic nuclei within the nuclear shell model

Quantum entanglement offers a unique perspective into the underlying structure of strongly-correlated systems such as atomic nuclei. In this paper, we use quantum information tools to analyze the structure of light and medium-mass berillyum, oxygen, neon and calcium isotopes within the nuclear shell model. We use different entanglement metrics, including single-orbital entanglement, mutual information, and von Neumann entropies for different equipartitions of the shell-model valence space and identify mode-entanglement patterns related to the energy, angular momentum and isospin of the nuclear single-particle orbitals. We observe that the single-orbital entanglement is directly related to the number of valence nucleons and the energy structure of the shell, while the mutual information highlights signatures of proton–proton and neutron–neutron pairing, as well as nuclear deformation. Proton and neutron orbitals are weakly entangled by all measures, and in fact have the lowest von Neumann entropies among all possible equipartitions of the valence space. In contrast, orbitals with opposite angular momentum projection have relatively large entropies, especially in spherical nuclei. This analysis provides a guide for designing more efficient quantum algorithms for the noisy intermediate-scale quantum era.

Generic size dependences of pairing in ultrasmall systems: electronic nano-devices and atomic nuclei

Generic size dependences of pairing in ultrasmall systems: electronic nano-devices and atomic nuclei