39K Nuclei Research Articles

A combined solid-state 1H, 13C, 17O NMR and periodic DFT study of hyperfine coupling tensors in paramagnetic copper(II) compounds

We report solid-state 1H, 13C, and 17O NMR determination of hyperfine coupling tensors (A-tensors) in several paramagnetic Cu(II) (d9, S = 1/2) complexes: trans-Cu(DL-Ala)2·H217O, Cu([1–13C]acetate)2·H2O, Cu([2–13C]acetate)2·H2O, and Cu(acetate)2·H217O. Using these new experimental results and some A-tensor data available in the literature for trans-Cu(L-Ala)2 and K2CuCl4·2H2O, we were able to examine the accuracy of A-tensor computation from a periodic DFT method implemented in the BAND program. We evaluated A-tensors on 1H (I = 1/2), 13C (I = 1/2), 14N (I = 1), 17O (I = 5/2), 39K (I = 3/2), 35Cl (I = 3/2), and 63Cu (I = 3/2) nuclei over a range spanning more than 3 orders of magnitude. We found that the BAND code can reproduce reasonably well the experimental results for both A-tensors and nuclear quadrupole coupling tensors.

Core-polarization effects on electron scattering in 10B, 19F and 39K nuclei

In the study of NN interactions, calculations are performed from the longitudinal shape factor through inelastic scattering of electrons. The determination of the longitudinal shape factor in the inelastic scattering of electrons is based on the transfer momentum and angular momentum. We delve into the analysis of electron scattering shape factors as well as CP — standing for nuclear polarization — in longitudinal inelastic shell models. This is done using NuShellX, where we employ a sum potential HO to look at 10B, 39K, and 19F nuclei. Among the computations carried out include those of Single Particle Matrix Elements and Inelastic Electron Scattering Shape Factors which are then pitted against experimental data. The outcomes depict a scenario where the model space provides a full explanation on NushellX shape factor compared to nuclear polarization; this thereby implies less contribution from certain quarters towards shaping this factor. On another front, the comparison shows that results from longitudinal form factor polarization for NuShellX core find resonance with what is already available experimentally— a pointer towards reliability if not outright correctness.

Investigation of the nuclear magnetic resonance spectra of potassium ions in aqueous solutions and estimation of the magnetic moment of the nucleus 39K

The problem of increasing the accuracy of determining the magnetic moment of the potassium 39K nucleus, which is used in studies of the norm and pathology of living tissues by nuclear magnetic resonance methods, is considered. The paper presents experimental results for determining the resonance frequency ratio of water protons and 39K nuclei for KCl and KNO3 solutions at concentrations from 0.5 to 2 mol/kg of water. NMR signals from water protons and potassium nuclei were recorded simultaneously, which minimizes random and systematic errors in determining the ratio of the resonance frequencies to units of the eighth sign. When extrapolating the content of potassium salts in water to zero concentrations for single ions in water, it was determined 21.4300226(10). Using the known data for the magnetic moment of the proton and the data for proton shielding in water, we obtained 0.390962111(18). Shielding of potassium ions in water was previously calculated in the work of Antisera and others. When using these data on the shielding of potassium ions in water, the magnetic moment of the potassium core was obtained 0.391471(8). The comparison of the new result for μ(39K) with the data of previous works is discussed.

GIANT M1 RESONANCE ON THE GROUND AND EXCITED STATES IN 2s1d-SHELL NUCLEI

The gamma decay of the resonance-like structures observed in the reaction of radiative capture of protons by the nuclei 22Ne, 26Mg, 30Si, 34,36S, and 38Ar in the region of excitation energies of 7…12 MeV was studied. The excitation functions of this reaction were measured. The resonance strengths in the energy range of the accelerated protons Ep = 1.0…3.0 MeV were determined. The obtained discrete distributions of the magnetic dipole γ-transitions on the ground and excited states for the nuclei of the 2s1d-shell have resonance character. Giant M1 resonance on the ground and excited states in the 23Na, 27Al, 31P, 35.37Cl, and 39K nuclei has been identified. The position of the M1 resonance on excited states coincides with that predicted by the Brink-Axel hypothesis for nuclei that are at the beginning of the subshell.

Interfacial Interactions Govern the Mechanisms of CO2 Absorption and Desorption on A2CO3-Promoted MgO (A = Na, K, Rb, and Cs) Absorbents

In this study, we investigated the detailed mechanisms of CO2 absorption and desorption on A2CO3-promoted MgO absorbents (A = Na, K, Rb, and Cs). We analyzed the materials formed at various stages of the absorbents during CO2 absorption and desorption by thermal decomposition-gas chromatography/mass spectroscopy, in situ IR spectroscopy, solid-state magic-angle spinning NMR spectroscopy on 13C, 23Na, 25Mg, and 39K nuclei, diffuse reflectance UV–vis spectroscopy, and in situ X-ray diffraction as well as the conventional thermogravimetric analysis, ex situ X-ray diffraction, and elemental distribution mapping by energy-dispersive X-ray analysis using scanning electron microscopy. The absorption of CO2 of the absorbents occurs in two steps. The first step is a fast process involving basic sites on the MgO surface formed by the interaction between A2CO3 and MgO. Because the basicity of these sites depends on the size of A ion, the kinetics and capacity of CO2 absorption and the desorption properties of this p...

Elastic Electron Scattering from 35Cl, 37Cl and 39K Nuclei

Elastic Electron Scattering from 35Cl, 37Cl and 39K Nuclei

Structural and thermodynamic properties of Tutton salt K2Zn(SO4)2·6H2O

The structural and thermodynamic properties of Tutton salt K2Zn(SO4)2·6H2O were investigated using thermogravimetric analysis, differential scanning calorimetry, and nuclear magnetic resonance. The first mass loss of H2O occurred around 353 K, which was interpreted as the onset of partial thermal decomposition, and the mass loss continues from T d to 440 K. The temperature dependences of the spin–lattice relaxation time for the 1H and 39K nuclei were measured in the laboratory frame and in the rotating frame. The results were compared with those obtained for the series of compounds, i.e., M2Zn(SO4)2·6H2O (M = Na, Rb, and Cs), that were previously reported.

Characterisation of magnesium potassium phosphate cements blended with fly ash and ground granulated blast furnace slag

Magnesium potassium phosphate cements (MKPCs), blended with 50wt.% fly ash (FA) or ground granulated blast furnace slag (GBFS) to reduce heat evolution, water demand and cost, were assessed using compressive strength, X-ray diffraction (XRD), scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR) spectroscopy on 25Mg, 27Al, 29Si, 31P and 39K nuclei. We present the first definitive evidence that dissolution of the glassy aluminosilicate phases of both FA and GBFS occurred under the pH conditions of MKPC. In addition to the main binder phase, struvite-K, an amorphous orthophosphate phase was detected in FA/MKPC and GBFS/MKPC systems. It was postulated that an aluminium phosphate phase was formed, however, no significant Al–O–P interactions were identified. High-field NMR analysis of the GBFS/MKPC system indicated the potential formation of a potassium-aluminosilicate phase. This study demonstrates the need for further research on these binders, as both FA and GBFS are generally regarded as inert fillers within MKPC.

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.

A nuclear magnetic resonance study of the structural properties and molecular motions of Li 2KH(SO 4) 2 and LiKSO 4 single crystals

The structural properties and relaxation mechanisms of Li 2KH(SO 4) 2 crystals were determined using the temperature dependences of NMR spectra and the spin–lattice relaxation times ( T 1) of their 1H, 7Li, and 39K nuclei. The results obtained were compared with the previously reported physical properties of LiKSO 4 crystals. The substitution of the potassium ions with protons in the LiKSO 4 crystals were variations in the phase transition temperatures, and the non-appearance of ferroelastic properties. The 7Li T 1 for the Li 2KH(SO 4) 2 crystals was much shorter than the 7Li T 1 for the LiKSO 4 crystals, and these findings indicate that the presence of the protons in Li 2KH(SO 4) 2 causes the Li ions to move with greater freedom.

Raman processes of KNaSO4 and K3Na(SO4)2 single crystals studied by 23Na and 39K nuclear magnetic resonance

AbstractThe spin–lattice relaxation rate, T, of the 23Na and 39K nuclei in KNaSO4 and K3Na(SO4)2 crystals was determined in the temperature range 160–420 K. The results showed similar temperature dependences of T for both types of nuclei, indicating that the local environment has an important influence on T of the metal nuclei. Moreover, the T values of the 23Na and 39K nuclei in the two crystals were found to increase with increasing temperature, and T was determined to be proportional to Tk for both metals. In the case of KNaSO4 and K3Na(SO4)2, T was found to have a temperature dependence proportional to T2, indicating that Raman processes may be responsible for the relaxation of the 23Na and 39K nuclei. Therefore, for the 23Na and 39K nuclei in the two crystals, Raman processes with k = 2 are more effective in nuclear quadrupole relaxation than direct processes.

A study of the electric quadrupole Raman processes of the proton‐conducting KHSeO4 and KDSeO4 single crystals using 1H, 2H and 39K NMR

AbstractThe spin–lattice relaxation time, T1, and the spin–spin relaxation time, T2, of the 1H, 2H, and 39K nuclei in KHSeO4 and KDSeO4 crystals were determined in the temperature range 160–420 K. The T1 of the 39K nuclei in the two crystals were found to decrease with increasing temperature, and the spin–lattice relaxation rate, T1–1, for 39K is proportional to Tk. In the case of KHSeO4, T1–1 for the 39K nuclei was found to have a very strong temperature dependence, i.e. it is proportional to T7. The temperature dependence of the 39K relaxation rate in KDSeO4 is in accordance with a Raman process, as T1–1 ∝ T2. Thus, for the 39K nuclei in the two crystals, Raman processes with k = 2 and 7 is due to the coupling of electric quadrupole moments to the thermal fluctuations of the local electric field gradients. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Study of the phase transitions by observation of the A and1H nuclear magneticresonance in ANH4SO4 (A = 7Li,39K and 87Rb) single crystals with excellent optical quality

ANH4SO4 (A = Li, K and Rb) single crystals were grown using the slow evaporationmethod. We studied the spectra, spin–lattice relaxation times,T1, and spin–spinrelaxation times, T2, of the 1H, 7Li, 39K and 87Rb nuclei in these three types of single crystals. The nuclear magnetic resonance observationsprovided a consistent description of the dynamics of the studied nuclei in these materials. TheT1 valuesfor the 1H nuclei are similar in all three crystals and the1H spin–lattice relaxation times increase with increasing temperature. However, as the radii ofthe metal ions increase, a corresponding decrease in the spin–lattice relaxation times of theA nuclei is observed. The differences observed in the spin–lattice relaxation times of the Anuclei upon changing the alkali-metal ion may be related to the ionic radius andthe lengths of the A–O bonds. Therefore, the occurrence of phase transitions inthese materials seems to be essentially dependent on the presence of the metalions.

A study of the ferroelastic phase transition of KH3(SeO3)2 single crystals using nuclear magnetic resonance

Relaxation times in KH3(SeO3)2 crystals were measured as functions of temperature. There are no significant changes in T1 for 1H and 39K nuclei at TC, except for a change in the number of proton and potassium signals. The role of structural changes in this transition is relatively minor. The transition is driven by the protons in the O(2)–H(2)–O(2) bonds, and the change in the number of resonance lines results from the crystal's ferroelastic properties. The results show that the ferroelastic phase transition is associated with the ordering of the O(2)–H(2)–O(2) hydrogens. The T1 and T2 of 1H in the O(2)–H(2)–O(2) bonds are liquid-like, i.e. of the order of milliseconds. In addition, 39K nuclear magnetic resonance results confirm that the phase of this crystal below TC is ferroelastic and that the phase above TC is paraelastic. These results are compared with those obtained for deuterated KD3(SeO3)2 crystals.

A nuclear magnetic resonance study of the ferroelastic phase transitions ofK3Na(CrO4)2 and K3Na(SeO4)2 single crystals

Nuclear magnetic resonance (NMR) measurements were carried out forK3Na(CrO4)2 and K3Na(SeO4)2 crystals over a range of temperatures. Two and three groups were observed in the23Na spectraof K3Na(CrO4)2 andK3Na(SeO4)2 crystals,respectively, which were found to become one group at the ferroelastic phase transition temperature,TC1. These transitions to one resonance line from two and three resonance lines are associated withthe crystals’ ferroelastic phase transitions. The changes in the spin–lattice relaxation times,T1, forthe 23Na and 39K nuclei in two crystals indicate that there is a structural phase transitionfrom the trigonal phase to the monoclinic phase in these crystals atTC1. Further, our results for the shifts in the resonance frequencies for the39K central resonance lines show that these ferroelastic phase transitionsare accompanied by shifts of the two crystallographically independentK+ cations, and mainly affect the environment of K(2), which is the most loosely bound cationin the crystal structures. We conclude that shifts of the oxygen atoms in thechromate and selenate groups around the Na and K atoms also play importantroles in these phase transitions. Therefore, the ferroelastic phase transitions inK3Na(CrO4)2 andK3Na(SeO4)2 crystalsat TC1 = 239 Kand TC1 = 334 K, respectively, are accompanied by slight changes in the respective geometries of theCrO4 and SeO4 tetrahedra around the Na and K atoms.

Total strength of the magnetic dipole resonance in 37Cl and 39K

The γ decay of resonance-like structures observed in the 36S(pγ)37Cl and 38Ar(pγ)39K reactions in the range of energies E p = 0.8–2.8 MeV of accelerated protons has been studied. The M1 resonance on the ground and excited states of 37Cl and 39K nuclei has been identified. The position of the centroid and the total strength of the M1 resonance on the ground state of these nuclei have been determined and explained taking into account pairing forces.

NMR study of the order–disorder phase transitions of KHCO 3 and KDCO 3 single crystals

KHCO 3 and its deuterated analogue KDCO 3 are typical materials that undergo order–disorder phase transitions at 318 and 353 K, respectively. The spin–lattice relaxation times, T 1, spin–spin relaxation times, T 2, and the number of resonance lines for the 1H, 2D, and 39K nuclei of these crystals were investigated using NMR spectrometer. These materials are known to exhibit anomalous decreases in T 1 near T C, which have been attributed to a structural phase transition. Additionally, changes in the symmetry of the (HCO 3) 2 2− (or (DCO 3) 2 2−) dimers in these materials are associated with large changes in T 1, T 2, and the number of resonance lines. Here we found that the resonance lines for 1H, 2D, and 39K nuclei decrease in number as the temperature is increased up to T C, indicating that the orientations of the (HCO 3) 2 2− (or (DCO 3) 2 2−) dimers and the environments of the K ions change at T C. Moreover, based on number of resonance lines, the results further indicate that the (HCO 3) 2 2− (or (DCO 3) 2 2−) dimers reorientate to approximately parallel to the directions of the hydrogen bonds (or deuteron bonds) and the direction of the a-axis. The transitions at 318 and 345 K of the two crystals are of the order–disorder type. The present results therefore indicate that the orientations of the (HCO 3) 2 2− and (DCO 3) 2 2− dimers and the environment of the K ion play a significant role in these phase transitions.

NMR studies of the new superconductors [formula omitted] ( [formula omitted], Rb)

We report results of nuclear magnetic resonance (NMR) experiments on 39K and 87Rb nuclei in the new superconductors AOs 2 O 6 ( A = K or Rb). These compounds crystallize in the β -pyrochlore structure. In the superconducting phase, we found a small peak in 1 / ( T 1 T ) for 87Rb slightly below the superconducting transition temperature ( T c ) but no peak for 39K. In the normal state of KOs 2 O 6 , we observed a clear pseudogap behavior similar to what has been observed in high T c cuprates.

1H and 39K spin–lattice relaxation, ionic motion and Raman processes in the proton conducting KHSeO 4 single crystal

The spin–lattice relaxation rates of 1H and 39K nuclei in KHSeO 4 crystals were studied in the temperature range 160–400 K. The spin–lattice relaxation recovery of 1H nucleus in this crystal can be represented with a single exponential function, and the relaxation T 1 −1 curve of 1H can be represented with the Bloembergen–Purcell–Pound (BPP) function. The relaxation process of 39K with dominant quadrupole relaxation can be described by a linear combination of two exponential functions. T 1 −1 for the 39K nucleus was found to have a very strong temperature dependence, T 1 −1= βT 7. Rapid variations in relaxation rates are associated with critical fluctuations in the electronic spin system. The T 7 temperature dependence of the Raman relaxation rate is shown here to be due to phonon–magnon coupling.

A study of the relaxation mechanism of aKAl(SO4)2·12H2O single crystal byobservation of its 39K and 27Al spin–lattice relaxation processes

The spin–lattice relaxation processes of the39K and27Al nucleiin KAl(SO4)2·12H2O crystals were studied; we found that these processes can be described by linearcombinations of two and three exponential functions, respectively. From these results, weconclude that the discontinuity in the curve of the spin–lattice relaxation rate nearTc (= 360 K) corresponds to the first-order phase transition of the crystal. In the case of the39K nucleus, the relaxation rate increases as the temperature increases. The relaxation rate of the27Al nucleus decreases belowTc as the temperatureincrease, while above Tc its relaxation rate increases with increasing temperature. The temperature dependences ofthese spin–lattice relaxation rates can be described with the power law . Least square fits of the relaxation rates at temperatures belowTc indicatethat k = 2 for the 39K nucleus and k = 7 for the 27Al nucleus. From these results, we conclude that the39K and 27Al spin–lattice relaxations occur from Raman relaxation processes.