11B Nuclei Research Articles

Effect of lithium concentration on the network connectivity of nuclear waste glasses

Structure of borosilicate glasses with varying Li2O contents were investigated using Magic Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR), employing 6Li, 11B, 23Na, 27Al and 29Si nuclei. 11B MAS NMR revealed that increasing Li2O contents result in formation of [BO4]− sites at the expense of BO3. 11B{6Li} and 27Al{6Li} dipolar heteronuclear multiple quantum correlation (D-HMQC) NMR revealed Li as a charge compensator for anionic tetrahedral sites with increased Li. 11B{6Li} J-coupling mediated HMQC NMR suggested the possible association of Li with non-bridging oxygens on Q2 and Q3 sites, indicating its dual role in the glass network. 29Si and 23Na MAS NMR spectra showed depolymerisation of the silicate network and shortening of Na-O bond lengths with increased Li. NMR results are supported by Raman spectroscopy and thermal analysis that indicate depolymerisation of the silicate network and a reduction in glass transition temperature at higher Li content.

Experimental Study of Cold Dense Nuclear Matter

The fundamental theory of nuclear interactions, Quantum Chromodynamics (QCD), operates in terms of quarks and gluons at higher resolution. At low resolution the relevant degrees of freedom are nucleons. Two-nucleon Short-Range Correlations (SRC) help to interconnect these two descriptions. SRCs are temporary fluctuations of strongly interacting close pairs of nucleons. The distance between the two nucleons is comparable to their radii and their relative momenta are larger than the fermi sea level. According to the electron scattering experiments held in the last decade, SRCs have far-reaching impacts on many-body systems, the nucleon-nucleon interactions, and nuclear substructure. The modern experiments with ion beams and cryogenic liquid hydrogen target make it possible to study properties of the nuclear fragments after quasi-elastic knockout of a single nucleon or an SRC pair. Here we review the status and perspectives of the SRC program in so-called inverse kinematics at JINR (Dubna, Russia). The first SRC experiment at the BM@N spectrometer (2018) with 4 GeV/c/nucleon carbon beam has shown that detection of an intact 11B nucleus after interaction selects out the quasi-elastic knockout reaction with minimal contribution of initial- and final-state interactions. Also, 25 events of SRC-breakups showed agreement in SRC properties as known from electron beam experiments. The analysis of the second measurement of SRC at BM@N held in 2022 with an improved setup is currently ongoing. The SRC project at JINR moved to a new experimental area in 2023, where the next measurement is being planned in terms of experimental setup and physics goals.

Nucleon and delute cluster transfer in the reactions 6Li + 9Be

The results of experiments on studying nucleon and cluster transfer processes in the reactions of the 6Li (68 MeV) ions with the 9Be target nuclei are presented. The angular distributions for the reaction channels 9Be(6Li,α)11Bg.s and 9Be(6Li,10B)5Heg.s. have been measured. To describe the possible contributions of sequential transfer of nucleons and alpha clusters, as well as direct transfer of the 5Не cluster, the DWBA method (FRESCO) is used, the spectroscopic amplitudes are obtained for the configurations of (9Be+d) and (6Li+5He) in the 11B nucleus and (6Li+α) in the 10B nucleus. The results of the theoretical analysis agree with the experimental data and indicate a strong correlation between a neutron and an α-cluster, leading to the formation of the 5Не cluster in the transfer processes.

Reaction rate of radiative capture of proton by 11B nucleus

Reaction rate of radiative capture of proton by 11B nucleus

Nanocomposite Polymer Gel Electrolyte Based on TiO2 Nanoparticles for Lithium Batteries.

In this article, the specific features of competitive ionic and molecular transport in nanocomposite systems based on network membranes synthesized by radical polymerization of polyethylene glycol diacrylate in the presence of LiBF4, 1-ethyl-3-methylimidazolium tetrafluoroborate, ethylene carbonate (EC), and TiO2 nanopowder (d~21 nm) were studied for 1H, 7Li, 11B, 13C, and 19F nuclei using NMR. The membranes obtained were studied through electrochemical impedance, IR-Fourier spectroscopy, DSC, and TGA. The ionic conductivity of the membranes was up to 4.8 m Scm-1 at room temperature. The operating temperature range was from -40 to 100 °C. Two types of molecular and ionic transport (fast and slow) have been detected by pulsed field gradient NMR. From quantum chemical modeling, it follows that the difficulty of lithium transport is due to the strong chemisorption of BF4- anions with counterions on the surface of TiO2 nanoparticles. The theoretical conclusion about the need to increase the proportion of EC in order to reduce the influence of this effect was confirmed by an experimental study of a system with 4 moles of EC. It has been shown that this approach leads to an increase in lithium conductivity in an ionic liquid medium, which is important for the development of thermostable nanocomposite electrolytes for Li//LiFePO4 batteries with a base of lithium salts and aprotonic imidasolium ionic liquid.

Synthesis, Structure, and Spectroscopy of the Biscarboranyl Stannylenes (bc)Sn·THF and K2[(bc)Sn]2 (bc = 1,1'(ortho-Biscarborane)) and Dibiscarboranyl Ethene (bc)CH=CH(bc).

Two compounds containing a Sn(II) atom supported by a bidentate biscarborane ligand have been synthesized via salt metathesis. The synthetic procedures for (bc)Sn·THF (bc = 1,1' (ortho-carborane) (1) and K2[(bc)Sn]2 (2) involved the reaction of K2[bc] with SnCl2 in either a THF solution (1) or in a benzene/dichloromethane solvent mixture (2). Using the same solvent conditions as those used for 2 but using a shorter reaction time gave a dibiscarboranyl ethene (3). The products were characterized by 1H, 13C, 11B, 119Sn NMR, UV-vis, and IR spectroscopy, and by X-ray crystallography. The diffraction data for 1 and 2 show that the Sn atom has a trigonal pyramid environment and is constrained by the bc ligand in a planar five-membered C4Sn heterocycle. The 119Sn NMR spectrum of 1 displays a triplet of triplets pattern signal, which is unexpected given the absence of a Sn-H signal in the 1H NMR, IR spectrum, and X-ray crystallographic data. However, a comparison with other organotin compounds featuring a Sn atom bonded to carboranes reveal similar multiplets in their 119Sn NMR spectra, likely arising from long-range nuclear spin-spin coupling between the carboranyl 11B and 119Sn nuclei. Compound 3 displays structural and spectroscopic characteristics typical of conjugated alkenes.

Electrically detected electron nuclear double resonance in amorphous hydrogenated boron thin films

We report on electrically detected electron nuclear double resonance (EDENDOR) observations via spin dependent trap assisted tunneling (SDTAT) in amorphous boron thin films at 250 K. We observe EDENDOR from both 10B and 11B nuclei, likely interacting with carbon impurities. In SDTAT, electron paramagnetic resonance (EPR) is detected through a change in the trap assisted tunneling current through the thin film. As in conventional electron nuclear double resonance (ENDOR) the ENDOR response is detected through a modest change in the EPR response. Since SDTAT detection sensitivity is about seven orders of magnitude greater than that of conventional EPR, it, in principle, can provide an enormous boost in ENDOR sensitivity. This enormous potential sensitivity improvement can be compromised by a coupling of the RF electromagnetic field driving the nuclear spin response and the electrical leads which are utilized to monitor the resonance induced changes in device current. We overcome this difficulty with the introduction of proportional-integral-derivative (PID) control of the RF circuitry which greatly suppresses fluctuations in the amplitude of the RF magnetic field at the thin film structure under investigation.

Deuteron scattering and (d,t) reaction on 11B at an energy of 14.5 MeV

At an energy of 14.5 MeV, the elastic and inelastic scattering of deuterons and the (d, t) reaction on 11B nuclei were studied. Experimental angular distributions with transitions to the states of the 11B nucleus (ground state (3/2−), 4.445 (5/2−) MeV, 6.743 (7/2−) MeV) and to the states of the 10B nucleus (ground state (3+), 0.718 MeV (1+), 1.74 MeV (0+, T = 1), 2.15 MeV (1+)) were analyzed by the coupled channel method. The value of the quadrupole deformation parameter β2= 0.80 ± 0.2 was extracted. The assumption of a direct mechanism for picking up a neutron in the reaction (d, t) made it possible to describe rather well the measured angular distributions for the states of the 10B nucleus. The values of the spectroscopic amplitudes for the transitions to these states have been extracted. It is shown that the mechanism of 8Be transfer both in the form of a whole cluster and in the sequential transfer of two α-particles does not play a significant role. It was found that the deformation of the 10B and 11B nuclei noticeably affects the calculated cross sections for the (d, t) reaction.

Specific features of capture reactions of real and virtual α-particles by 6Li and 7Li isotopes

The article examines the features of the interaction of virtual and real α-particles with isotopes 6Li and 7Li with the formation of the ground and excited states of 10B and 11B nuclei. The multiparticle shell model is used to describe the structures of nuclei. The significant difference in the excitation spectra of 10B and 11B nuclei in the capture of real and virtual α-particles is explained by the structural features of these nuclei and different mechanisms of capture of α-particles. Real α-particles are captured in reactions (α, γ), and virtual ones - in lithium cluster transfer reactions. In both boron isotopes, the first decay channel is the α-particle, then there is an energy range of several MeV until the next decay channel with the emission of particles. Moreover, in this energy range, the S-factors are anomalously small. If the excited levels lie above the threshold for the breakup of the nucleus with the emission of certain particles a, then the S-factors turn out to be related to the partial widths of the decay Га. In contrast to spectroscopic factors, which do not depend on energy and are determined only by the structure of the initial and final states, the partial Γ-widths depend on the energy which the particles are emitted with. It is shown that, in a narrow energy range from the first threshold for the emission of particles to the second threshold, the cross sections for the excitation of residual nuclei by real and virtual α-particles differ significantly. Narrow beams of γ-quanta formed with large cross sections in reactions of radiative α-capture can be used for diagnostics of thermonuclear plasma.

Nuclear magnetic relaxation studies of BH4 in metal Borohydrides

AbstractA different approach of nuclear magnetic resonance (NMR) relaxation of the rotational motion of BH4 tetrahedron in light metal borohydrides was introduced. Previous NMR relaxation studies were mainly performed using an approximation which is based on a single exponential transition approach for the spin–lattice relaxation of the spin under quadrupolar interaction. In this new approach, a relaxation rate equation was derived by strictly taking into account both electric quadrupolar and magnetic dipolar contributions to the transitions between Zeeman energy states of quadrupolar 11B nucleus that was coupled to many proton spins. Two exponential relaxation times derived from our theoretical treatment were applied to the analysis of 11B spin–lattice relaxation of LiBH4 and Ca(BH4)2. The activation energies and the correlation times of the reorientational motions of BH4 were evaluated from the two experimental spin–lattice relaxation times. The results were compared to previous activation energies and correlation times.

Further investigation of 10,11B + 58Ni elastic scattering

The recently measured 10,11B + 58Ni elastic scattering angular distributions are subjected to thorough analysis using different potentials such as optical and double folding, based on the CDM3Y6, with and without taking into account the effect of the rearrangement term, as well as the cluster folding potential. The cluster structure for 10B (11B) as composed of 6Li (7Li) core with an alpha particle orbiting this core is hence studied. The experimental data for the 10,11B + 58Ni nuclear systems are fairly reproduced with all the aforementioned potentials. The renormalization factors for the real double folded potential (N r ) indicate the need to reduce the strength of the produced potentials by ∼ 50% and ∼ 36% to reproduce the considered data for the 10B + 58Ni and the 11B + 58Ni nuclear systems, respectively. As a result of applying a rearrangement term to the double folding potential, a small change can be observed in the N r values. Cluster folding analysis for the 10B + 58Ni elastic scattering cross sections reveals a similar trend; the strength of the renormalization factor for the real part of the potential constructed based on the cluster folding model ( N RCF ) needs to be reduced by ∼ 48%. The observed reduction in the strength of the constructed double and cluster folding potentials reflects the weak binding nature of the 10B and 11B nuclei. It was somewhat surprising that the extracted N RCF = 1.24 ± 0.064 for the 11B + 58Ni system.

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.

Symmetrized Normal Mode Analysis of the Spin–Lattice Relaxation in Solid Calcium Borohydride

The symmetrized normal mode analysis presented in a previous paper was used to analyze the 11B spin–lattice relaxation of solid calcium borohydride. From the analytical results, the quadrupolar and the dipolar spectral densities and reorientational correlation times of various relaxation interactions were evaluated. Based on the spectral densities, the quadrupolar contribution to the spin–lattice relaxation of 11B nucleus was calculated. As expected from the QCC value of 11B nucleus in solid calcium borohydride, the ratio of the quadrupolar contribution to the dipole–dipole contribution in the 11B spin–lattice relaxation was proved to be higher than 30% at 100°C. The symmetrized normal mode could be a useful method for the interpretation of AX4 spin system containing a quadrupolar nucleus, and thus the determination of the motional parameters of BH4 unit in solid calcium borohydride.

Fly ash–GGBS geopolymer in boron environment: A study on rheology and microstructure by ATR FT-IR and MAS NMR

The present study focuses on the use of borax composite sodium silicate activator (B) in place of water glass (S) in the fly ash–GGBS composite (4:1) geopolymerization. The substituent is favoured as it delivers advantages such as increased setting time and workability by mitigating the agglomeration of flocks without affecting the compressive strength of the geopolymer. Microstructural changes of boroaluminosilicate were studied with the help of ATR-FT-IR and MAS NMR. Rheology studies indicated that the borax composite pastes display shear thinning behaviour with low yield stress and fit well with the Bingham model. In-situ ATR-FT-IR spectrum revealed the severing of silica bonds by soluble [BO4] and its incorporation into the silicate backbone resulted in the drop in of Si–O–T asymmetry vibration response. The NMR spectral changes of 29Si,27Al and 11B nuclei environment in geopolymeric tetrahedral network showed that the fraction of [SiO4] and [BO4] increases upon borax addition with the diminished fraction of B3 non-rings without any specific changes in Al coordination. The tetrahedral boron absorption band in the wave numbers at 1380–1310 cm−1 and1134 cm–1is observed in FT-IR and its configuration is compatible in the reaction product.

Studying the Cluster Structure of the 11B Nucleus

Excitation spectra of the 11В nucleus in the lithium reaction of deuteron and α-particle cluster transfer are calculated by summing corresponding spectroscopic S-factors in the multiparticle shell model. It is shown that the difference between the excitation spectra of the 11В nucleus in lithium reactions of α-cluster transfer on the 7Li nucleus and the reaction of 7Li(α, γ)11B radiative capture is due to specific structural features of the states of the 11В nucleus in the near-threshold region.

Analysis of α+11B elastic and inelastic scattering using microscopic and semi-microscopic representations

In the present study angular distributions of the differential cross section for elastic and inelastic scattering of alpha (α)-particles of 11В nuclei at different bombarding energies have been analyzed in the framework of the optical model (OM) potential. Two OM folding approaches were adopted in order to construct the real part of the α-nucleus potential. First, we generated the semi-microscopic single folding (SF) potential by folding an effective α-nucleon (α-N) interaction over the nuclear matter density of the target (11B) nucleus. In addition, the double folding (DF) approach was employed in order to deduce a microscopic representation of the optical potential by folding an effective density-dependent (DDM3Y) nucleon–nucleon interaction over the matter densities of the colliding nuclei. Successful theoretical predictions of six sets of experimental elastic scattering data have been obtained over the whole measured angular range. However, it was found that introducing real renormalization coefficients (∼0.9–1.6) is essential in order to obtain best fits with data. On the other side, sixteen sets of the inelastic scattering data at several excited states of 11B nucleus were analyzed using the constructed SF and DF deformed potentials. In general, reasonable description of the data is obtained. However underestimated predictions of data were obtained at backward measured angles. The deduced reaction (absorption) cross sections and nuclear deformation lengths were also investigated.

A Modified Townes-Dailey Model for Interpretation and Visualization of Nuclear Quadrupole Coupling Tensors in Molecules

We propose a modified Townes-Dailey (TD) model to help interpret and visualize experimentally measureable nuclear quadrupole coupling tensors (thus the electric field gradient tensors) in molecules. We show that, within the framework of the TD model, each principal component of the nuclear quadrupole coupling tensor is directly related to a new quantity termed as the valence p-orbital population anisotropy (VPPA or ΔP) in the same direction. While the proposed model is a simple reformulation of the original TD model thus does not introduce new physics, the concept of VPPA makes it possible to directly interpret as well as visualize, in a much straightforward way, the experimentally determined nuclear quadrupole coupling tensors in molecules. We illustrate the utilization of VPPA using nuclear quadrupole coupling tensors for 11B, 14N, 17O, 35Cl, 87Br, and 127I nuclei in a variety of molecules. We propose to use VPPA or ΔP ellipsoid representation as a means of visualizing/displaying nuclear quadrupole coupling tensors in the molecular frame. We show the usefulness of the VPPA concept in providing a unifying explanation for seemingly different types of molecular interactions such as hydrogen bonding, halogen bonding, and frustrated Lewis pairs. We further suggest that VPPA can be used as a universal measure of the ability of any element in the entire p-block of the periodic table (groups 13-16) to interact with nucleophiles (e.g., formation of chalcogen, pnictogen, tetrel, and triel bonds).

8He spectroscopy in stopped pion absorption by 11B nuclei

Level structure of 8He has been studied in the reaction of stopped pion absorption by 11B nuclei 11B(π−,pd)X. The experiment was carried out at the LANL with a two-arm semiconductor spectrometer. The missing mass spectrum in the range 0 MeV < MM < 50 MeV has been described by the superposition of phase-space distributions and the six states of 8He. Parameters of these states have been compared with data of other experimental and theoretical works.

Total reaction cross sections of neutron-rich light nuclei measured by the COMBAS fragment-separator

Preliminary results of measurements of the total reaction cross sections σR for nuclei 4He, 6He, 8He, 7Li, 8Li, 9Li, 1Li, 11Be, 9Be, 10Be, 11Be, 12Be, 8B, 10B, 11B and 12B nuclei at energy range (10-50) A MeV with 28Si target is presented. The secondary beams of light nuclei were produced by bombardment of the 15N (50 A MeV) primary beam on Be target and separated by COMBAS fragment-separator. In dispersive focal plane a horizontal slit defined the momentum acceptance as 1% and a wedge degrader of 600 μm Al was installed. The Bρ of the second section of the fragment-separator was adjusted for measurements in energy range (10-45) A MeV. The strong absorption model reproduces the A-dependence of ψR, but not the detailed structure. We are comparing our experimental data with predictions of microscopic (dashed line) and strong absorption model, Glauber multiple scattering theory and preliminary results are obtained.

Symmetrized Normal Mode Analysis of the Spin–Lattice Relaxation of Metal Borohydrides in Solids

The spin–lattice relaxation of a quadrupolar nucleus 11B of solid borohydrides was measured by using solid‐state NMR techniques and the experimental data were analyzed with a newly‐constructed relaxation matrix. The spectral densities for dipole–dipole, quadrupolar, and random‐field interactions were obtained, and the quadrupolar contribution to the spin–lattice relaxation of 11B nucleus of solid borohydrides were calculated as well. The quadrupolar contribution was less than 10% in solid LiBH4, as has been reported. In addition, the quadrupolar contribution was more than 30% in solid Mg(BH4)2, as was expected. The symmetrized normal mode analysis for the spin–lattice relaxation of a quadrupolar nucleus could provide more accurate spectroscopic parameters, and is expected to improve accuracy of the description of the rotational motion of the local chemical unit containing the quadrupolar nucleus.