Cs Nuclei Research Articles

Hydration, self-diffusion and ionic conductivity of Li+, Na+ and Cs+ cations in Nafion membrane studied by NMR

Hydration of Nafion 117 perfluorinated sulfonic cation-exchange membrane in alkaline ion forms was investigated by high resolution 1H NMR. Hydration numbers of Li+, Na+ and Cs+ cations were 5 ± 1, 6 ± 1 and 1 ± 0.2, correspondingly for membrane equilibrated with water vapor at 98% RH. As opposed to Li+ and Na+, which form separate ion pair, Cs+ cation directly contacts with membrane sulfonate group. Cation self-diffusion coefficients were measured by pulsed field gradient NMR technique on 7Li, 23Na and 133Cs nuclei for the first time. Self-diffusion coefficients are changed in the next rows Li+ ≤ Na+ > Cs+. Self-diffusion activation energies of Li+ and Na+ cations are about 20 kJ/mol which is close to water self-diffusion activation energy in these membranes, but Cs+ self-diffusion activation energy is distinctly more (25 kJ/mol). Ionic conductivities calculated on the basis of Nernst–Einstein equation from cation self-diffusion coefficients 1.6∙10−2, 2∙10−2, 6∙10−3 S/cm for Li+, Na+, Cs+ cations, correspondingly, are closely approximating to conductivities measured by impedance spectroscopy: 1.3∙10−2, 1.1∙10−2, 2.3∙10−3 S/cm for Li+, Na+, Cs+ cations, correspondingly, but calculated values are appreciably more compared with experimental meanings.

Study of the Nuclear Structure for Some Target Nuclei Used in the Production of Beta-Emitting Radioactive Isotopes for the Fabrication of Nuclear Batteries

The nuclear structure of 40Ar, 112Cd, 133Cs, 151Eu, 154Sm, and 226Ra target nuclei used in nuclear battery technology was investigated. These nuclei are widely used for the radioisotope thermo-electric generator space studies and for betavoltaic battery microelectronic systems. For this purpose, some nuclear static properties were calculated. In particular, the single particle radial nuclear density distribution, the corresponding root mean square radii, neutron skin thicknesses, and binding energies were calculated within the framework of Hartree-Fock approximation with Skyrme interaction. The bremsstrahlung spectra produced by the absorption of beta particles through the betavoltaic process and backscattered photons spectrum were also studied. All the obtained results were compared with available experimental data.

Hydration and Diffusion of H+, Li+, Na+, Cs+ Ions in Cation-Exchange Membranes Based on Polyethylene- and Sulfonated-Grafted Polystyrene Studied by NMR Technique and Ionic Conductivity Measurements.

The main particularities of sulfonate groups hydration, water molecule and alkaline metal cation translation mobility as well as ionic conductivity were revealed by NMR and impedance spectroscopy techniques. Cation-exchange membranes MSC based on cross-linked sulfonated polystyrene (PS) grafted on polyethylene with ion-exchange capacity of 2.5 mg-eq/g were investigated. Alkaline metal cation hydration numbers (h) calculated from temperature dependences of 1H chemical shift of water molecule for membranes equilibrated with water vapor at RH = 95% are 5, 6, and 4 for Li+, Na+, and Cs+ ions, respectively. These values are close to h for equimolar aqueous salt solutions. Water molecules and counter ions Li+, Na+, and Cs+ diffusion coefficients were measured by pulsed field gradient NMR on the 1H, 7Li, 23Na, and 133Cs nuclei. For membranes as well as for aqueous chloride solutions, cation diffusion coefficients increased in the following sequence: Li+ < Na+ < Cs+. Cation and water molecule diffusion activation energies in temperature range from 20 °C to 80 °C were close to each other (about 20 kJ/mol). The cation conductivity of MSC membranes is in the same sequence, Li+ < Na+ < Cs+ << H+. The conductivity values calculated from the NMR diffusion coefficients with the use of the Nernst–Einstein equation are essentially higher than experimentally determined coefficients. The reason for this discrepancy is the heterogeneity of membrane pore and channel system. Ionic conductivity is limited by cation transfer in narrow channels, whereas the diffusion coefficient characterizes ion mobility in wide pores first of all.

Chemical Shift and Second‐Order Quadrupolar Effects in the Solid‐State 133Cs NMR Spectra of [Cs+(Cryptand[2.2.2])]X (X = I−, SCN−·H2O)

[Cs+(Cryptand[2.2.2])]I− (1; Cryptand[2.2.2] = C222) was characterized via single‐crystal X‐ray diffraction and was shown to crystallize in the monoclinic space group I2/c system with a = 8.9605 (2), b = 23.5073 (5), c = 11.7563 (3) Å, and β = 93.792 (2)°. Stationary and magic angle spinning (MAS) experiments under different magnetic fields allowed for the separation of the chemical shift and quadrupole coupling tensor parameters. Remarkably, MAS spectra showing pure second‐order quadrupole powder patterns at 4.23 T were observed for 133Cs nuclei with small quadrupole moments owing to the large electric field gradients (EFGs) caused by short CsO and CsN bond distances in the [Cs+(C222)] ions. Stationary NMR powder patterns with a combination of the chemical shifts and second‐order quadrupolar interactions were observed. The EFG and chemical shift tensor components calculated using the atomic coordinate files and Gaussian 09 were reasonably consistent with the experimental values.

Structure of odd-odd Cs isotopes within the interacting boson-fermion-fermion model based on the Gogny-D1M energy density functional

The spectroscopic properties of the odd-odd isotopes $^{124-132}$Cs have been studied within the interacting boson-fermion-fermion model based on the Gogny-D1M energy density functional framework. Major ingredients to build the interacting boson-fermion-fermion Hamiltonian, such as the ($\beta,\gamma$)-deformation energy surfaces for the even-even core nuclei $^{124-132}$Xe as well as single-particle energies and occupation probabilities of the odd nucleons, have been computed microscopically with the constrained Hartree-Fock-Bogoliubov method. A few coupling constants of the boson-fermion and residual neutron-proton interactions are fitted to reproduce with a reasonable accuracy the experimental excitation energy of the low-lying levels of the odd-mass and odd-odd nuclei. The method is applied to describe the low-energy low-spin spectra of the odd-odd Cs nuclei and the band structures of higher-spin higher-energy states, mainly based on the $(\nu h_{11/2})^{-1}\otimes\pi h_{11/2}$ configuration. Many of those odd-odd Cs nuclei have been identified as candidates for exhibiting chiral doublet bands.

A study of nuclear structure properties of even and odd 103–140Sb, 105–143Te, 107–145I, 109–148Xe and 112–151Cs nuclei in the axial deformation

We investigated ground-state nuclear structure properties of even and odd [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] nuclei via the axially deformed solution of Skyrme Hartree–Fock Bogoliubov (HFB) based on the transformed harmonic oscillator (THO) and the harmonic oscillator. In the calculations, different Skyrme force parameters were used to obtain wide nuclear data of the nuclei. The calculated results were compared with the results of the experimental data and theoretical models, i.e., the finite-range liquid-drop model (FRDM) and relativistic mean-field theory (RMFT). Additionally, the deformation regions of neutron rich Sb, Te, I, Xe and Cs nuclei have also been discussed. Moreover, in addition to the binding energy per particle, charge, proton and neutron density radii, one-neutron [Formula: see text], and two-neutron separation energies [Formula: see text], the quadropule deformation parameter [Formula: see text], the neutron skin thicknesses (NST), the quadrupole moments [Formula: see text] and the pairing gap energies of the nuclei were determined by HFBTHO 2.00 code.

Local environments for Cs(1) and Cs(2) sites in a perovskite Cs2CoBr4 single crystal with a dominant magnetic type based on the observed spin-lattice relaxation time

The local structure and molecular motion for 133Cs in a Cs2CoBr4 single crystal were examined by using the spin-lattice relaxation time from nuclear magnetic resonance (NMR). The two inequivalent Cs(1) and Cs(2) sites surrounded by Br ions in Cs2CoBr4 were clearly distinguished by using 133Cs NMR spectra. The spin-lattice relaxation times T1 of the Cs(1) and Cs(2) nuclei in Cs2CoBr4 were obtained, and the temperature dependence of the relaxation time for Cs(2) changed more abruptly than that for Cs(1). The T1 values for Cs(1) and Cs(2) ions were used to determine the activation energies for the molecular motions, and the molecular motion of Cs(2) surrounded by nine bromide ions was tighter than that of Cs(1) surrounded by 11 bromide ions.

Electronic structure and quadrupole interactions in triple molybdates Li2M3Al(MoO4)4, M = Cs, Rb

Within the density functional theory the electronic structure of triple molybdates Li2M3Al(MoO4)4, where M = Cs, Rb, is studied for the first time. It is found that all molybdates studied belong to wide band insulators with a band gap of ~4 eV. Quadrupole frequencies and asymmetry parameters of the electric field gradient near magnetic 7Li, 27Al, 87Rb, and 133Cs nuclei are calculated and experimental NMR spectra are interpreted.

Crystal growth and thermal properties of the Tutton salt Cs2Fe(SO4)2·6H2O single crystal

Thermal properties and phase transitions of the Tutton salt Cs2Fe(SO4)2·6H2O were investigated using thermogravimetric analysis, differential scanning calorimetry, and nuclear magnetic resonance (NMR). The first occurrence of mass loss is at approximately 321 K (=Td) and is interpreted as being the onset of partial thermal decomposition. Phase transitions were observed at 356 K (=TC1) and 450 K (=TC2). The temperature dependence of the NMR spectrum and spin–lattice relaxation time T1 for the 133Cs nuclei abruptly changes near TC1. These changes are associated with changes in the geometry of the water and five SO4 oxygens around the Cs ions.

NMR in Li2 M 3Al(MoO4)4 triple molybdates (M = Rb, Cs)

Nuclear magnetic resonance (magic angle spinning) spectra of 7Li, 27Al, 87Rb, and 133Cs nuclei are measured in Li2M3Al(MoO4)4 triple molybdates (M = Rb, Cs) for the first time. Analysis of the nuclear magnetic resonance spectra reveal considerable asymmetry in the distribution of the electric charge throughout the crystal lattices of the compounds.

Medium-spin states in135Cs

Limited information is currently known on medium- and higher-spin states for ${}^{135}$Cs, a neutron-rich nucleus amenable to shell-model calculations due to its proximity to the shell closures in ${}^{132}$Sn. In order to extend the level structure of ${}^{135}$Cs to higher excitations, this nucleus was studied via prompt $\ensuremath{\gamma}$-ray spectroscopy of fragments following the fission of the compound nucleus ${}^{226}$Th formed in the ${}^{18}$O (91 MeV) $+$ ${}^{208}$Pb fusion-fission reaction. Medium-spin states up to spin (23/2) and $\ensuremath{\sim}$3.3 MeV excitation energy have been established. The observed states were compared with those in the neighboring $N=82$${}^{137}$Cs nucleus, as well as with states in the neighboring $N=80$ isotones. The coupling of the odd proton occupying the ${g}_{7/2}$ orbital to the yrast states in the ${}^{134}$Xe and ${}^{136}$Ba cores could account for the lower excited states of ${}^{135}$Cs. The experimental results are compared with predictions from shell-model calculations.

High-spin structures of55136Cs81

Odd-odd ${}^{136}$Cs nuclei have been produced in the ${}^{18}\mathrm{O}+{}^{208}$Pb and ${}^{12}\mathrm{C}+{}^{238}$U fusion-fission reactions and their $\ensuremath{\gamma}$ rays studied with the Euroball array. The high-spin level scheme was built up to $\ensuremath{\sim}$4.7 MeV excitation energy and spin $I\ensuremath{\sim}16\ensuremath{\hbar}$ from the triple $\ensuremath{\gamma}$-ray coincidence data. The configurations of the three structures observed above $\ensuremath{\sim}$2 MeV excitation energy are first discussed by analogy with the proton excitations identified in the semimagic ${}^{137}$Cs${}_{82}$ nucleus, which involve the three high-$j$ orbits lying above the $Z=50$ gap, $\ensuremath{\pi}{g}_{7/2}$, $\ensuremath{\pi}{d}_{5/2}$, and $\ensuremath{\pi}{h}_{11/2}$. This is confirmed by the results of shell-model calculations performed in this work.

Classical bifurcation in a quadrupolar NMR system

The Josephson Junction model is applied to the experimental implementation of classical bifurcation in a quadrupolar Nuclear Magnetic Resonance system. There are two regimes, one linear and one nonlinear which are implemented by the radio-frequency term and the quadrupolar term of the Hamiltonian of a spin system respectively. Those terms provide an explanation of the symmetry breaking due to bifurcation. Bifurcation depends on the coexistence of both regimes at the same time in different proportions. The experiment is performed on a lyotropic liquid crystal sample of an ordered ensemble of $^{133}$Cs nuclei with spin $I=7/2$ at room temperature. Our experimental results confirm that bifurcation happens independently of the spin value and of the physical system. With this experimental spin scenario, we confirm that a quadrupolar nuclei system could be described analogously to a symmetric two--mode Bose--Einstein condensate.

A multinuclear solid state NMR, density functional theory and X-Ray diffraction study of hydrogen bonding in Group I hydrogen dibenzoates

An NMR crystallographic approach incorporating multinuclear solid state NMR (SSNMR), X-ray structure determinations and density functional theory (DFT) are used to characterise the H bonding arrangements in benzoic acid (BZA) and the corresponding Group I alkali metal hydrogen dibenzoates (HD) systems. Since the XRD data often cannot precisely confirm the proton position within the hydrogen bond, the relationship between the experimental SSNMR parameters and the ability of gauge included plane augmented wave (GIPAW) DFT to predict them becomes a powerful constraint that can assist with further structure refinement. Both the 1H and 13C MAS NMR methods provide primary descriptions of the H bonding via accurate measurements of the 1H and 13C isotropic chemical shifts, and the individual 13C chemical shift tensor elements; these are unequivocally corroborated by DFT calculations, which together accurately describe the trend of the H bonding strength as the size of the monovalent cation changes. In addition, 17O MAS and DOR NMR form a powerful combination to characterise the O environments, with the DOR technique providing highly resolved 17O NMR data which helps verify unequivocally the number of inequivalent O positions for the conventional 17O MAS NMR to process. Further multinuclear MAS and static NMR studies involving the quadrupolar 7Li, 39K, 87Rb and 133Cs nuclei, and the associated DFT calculations, provide trends and a corroboration of the H bond geometry which assist in the understanding of these arrangements. Even though the crystallographic H positions in each H bonding arrangement reported from the single crystal X-ray studies are prone to uncertainty, the good corroboration between the measured and DFT calculated chemical shift and quadrupole tensor parameters for the Group I alkali species suggest that these reported H positions are reliable.

Multinuclear magnetic resonance study of N-phenyl-aza-15-crown-5 complexes with lithium, sodium and caesium ions in nonaqueous solvents

Nuclear magnetic resonances of 7Li, 23Na and 133Cs nuclei were used to study the lithium, sodium and caesium ion complexes with N-phenyl-aza-15-crown-5 (PhA15C5) in nitromethane (NM), acetonitrile (AN) and AN–NM mixture solutions. The chemical shift data indicated that these cations form 1 : 1 cation : ligand complexes with PhA15C5. The formation constants of the resulting complexes were calculated from the computer fitting of the chemical shift–mole ratio data. The results show that the complex formation constants of PhA15C5 with these cations vary in the order of Na+ > Li+ ≫ Cs+. Complexation of the lithium ion was also studied in binary AN–NM mixtures. It was found that the stability of the resulting complexes increases by an increase in the amount of NM in the solvent mixture.

2H and 133Cs nuclear magnetic resonance study of Cs3D(SO4)2 single crystals in laboratory and rotating frames

To understand the physical properties of Cs3D(SO4)2 single crystals, in which deuterium replaces hydrogen, the temperature dependence of the NMR spectrum and the spin–lattice relaxation times in the laboratory frame, T1, and in the rotating frame, T1ρ, for 2H and 133Cs are investigated using Fourier transform nuclear magnetic resonance spectrometry. Our results for the 2H and 133Cs relaxation times provide no evidence of a phase transition. The strong temperature dependence of the 2H resonance lines is associated with deformation of the H(SO4)2− tetrahedra. Further, T1 and T1ρ for the 2H and 133Cs nuclei are governed by different mechanisms, which we discuss in terms of fast and slow motion.

1H and 133Cs nuclear magnetic resonance study of the NH4 and Cs occupation rates of mixed (NH4)2−xCsxZnCl4 (x = 0, 1, and 2) crystals

The NMR spectra and the spin–lattice relaxation times, T1, of the 1H and 133Cs nuclei in (NH4)2−xCsxZnCl4 (x=0, 1, and 2) single crystals were determined by using NMR spectroscopy. We investigated the crystallographic structures of these crystals by determining the NH4 and Cs occupation probabilities of the two cationic sites. Our NMR experimental results confirm that in (NH4)2ZnCl4 there are two crystallographically inequivalent NH4 groups, NH4(1) and NH4(2), occupying the A1 and A2 sites, and that in Cs2ZnCl4 there are two crystallographically inequivalent Cs ions, Cs(1) and Cs(2), occupying the A1 and A2 sites. Both types of NH4 ions and both types of Cs ions are found in mixed NH4CsZnCl4 crystals; the occupation rates of the two different sites are 1 and 1 for Cs(1) and Cs(2), respectively, and 1 and 1 for NH4(1) and NH4(2), respectively.

Hyperpolarization of133Cs nuclei enhanced by ion movement in a cesium salt

Hyperpolarization of ${}^{133}$Cs nuclei in CsCl salt is achieved through spin transfer from an optically pumped Cs vapor, with maximum polarizations of 0.1$%$ demonstrated. Motional narrowing of the enhanced NMR line indicates that ion movement facilitates this process by transporting spin-polarized ions from the interface into the salt. The resulting NMR enhancement allows measurement of the polarization and its dynamics in real time. Based upon the NMR frequency and the longitudinal spin relaxation time, we find no evidence that the salt is contaminated by Cs metal or paramagnetic impurities. The Cs nuclear polarization reported here could be improved several orders of magnitude by intense laser heating of the entire sample.

NMR relaxation study of the phase transitions and relaxation mechanisms of the alums MCr(SO 4) 2·12H 2O ( M=Rb and Cs) single crystals

The physical properties and phase transition mechanisms of MCr(SO 4) 2·12H 2O ( M=Rb and Cs) single crystals have been investigated. The phase transition temperatures, NMR spectra, and the spin-lattice relaxation times T 1 of the 87Rb and 133Cs nuclei in the two crystals were determined using DSC and FT NMR spectroscopy. The resonance lines and relaxation times of the 87Rb and 133Cs nuclei undergo significant changes at the phase transition temperatures. The sudden changes in the splitting of the Rb and Cs resonance lines are attributed to changes in the local symmetry of their sites, and the changes in the temperature dependences of T 1 are related to variations in the symmetry of the octahedra of water molecules surrounding Rb + and Cs +. We also compared these 87Rb and 133Cs NMR results with those obtained for the trivalent cations Cr and Al in MCr(SO 4) 2·12H 2O and MAl(SO 4) 2·12H 2O crystals.

Elucidating the Time Scale and Geometry of Phosphate and Phosphonate Rotation in Solid Acid Electrolytes Using Multinuclear NMR

The dynamics of the anions in a series of solid acid electrolyte materials have been determined using solid-state 31P CODEX NMR. The time scale and activation energy of the phosphate reorientation were quantified; however, the characterization proved to be nontrivial due to interactions with the quadrupolar 133Cs nuclei. The series of compounds studied included other known proton conductors, where the alkali cation was replaced systematically with Rb+, Tl+, or K+. The nuclear properties of the cations, together with the relative proton conductivities of these electrolyte analogues, allowed for a complete analysis of the interactions (both structure reorientations and spin dynamics) giving rise to the observed CODEX buildup curves. The high-temperature super-protonic transition, and the narrow range of thermal stability, limits the usefulness of cesium dihydrogen phosphate (CDP) in fuel cell applications. With the goal of achieving a broader range of thermal stability and enhanced proton dynamics, the phos...