Nmr Study in Sodium-Hydrogen-C60 Superconductor

1998 ◽  
Vol 513 ◽  
Author(s):  
H. Ogata ◽  
S. Miyajima ◽  
K. Imaeda ◽  
H. Inokuchi
Keyword(s):  
Quadrupole Coupling Constant ◽  
Peak Position ◽  
Coupling Constant ◽  
Nmr Studies ◽  
Nmr Spectrum ◽  
H Nmr ◽  
Nmr Study ◽  
First Order Phase Transition ◽  
Quadrupole Coupling ◽  
First Order Phase

ABSTRACT23Na and 1H NMR studies have been carried out for a NaxHyC60 superconductor The peak position of the 23Na NMR spectrum exhibits discontinuous upfield shift of 30 ppm at about 250 K, indicates a first order phase transition From the line shape of the 23Na spectrum obtained at 7 K, the quadrupole coupling constant tensor is evaluated to be |e2Qq/h|=3.7 MHz with the asymmetry parameter η = 0.95. The 1H NMR spectrum suggests an anionic hydrogen state with weakly delocalized nature.

scholarly journals Proton and Deuteron NMR Study on Single Crystals of Na2ZnCl4 · 3 H2O (Na2ZnCl4 · 3 D2O)

1973 ◽  
Vol 28 (12) ◽  
pp. 1919-1931
Author(s):  
Alarich Weiss ◽  
A. Wüst
Keyword(s):  
Principal Axis ◽  
Quadrupole Coupling Constant ◽  
Coupling Constant ◽  
Gradient Tensor ◽  
H Nmr ◽  
Nmr Study ◽  
Nuclear Quadrupole Coupling Constant ◽  
Quadrupole Coupling ◽  
Direction Cosines ◽  
Nuclear Quadrupole

Single crystal 1H- and 2H-XMR spectra of Na2ZnCl4 · 3 H2O and Xa2ZnCl4 · 3 D2O, respectively, were studied. The following results have been obtained: The positions of the hydrogens and deuterons are described in the space group C23v- P 31m with one formula unit in the unit cell. The point positions are: HI(DI) in 3m: x = 0.455 ± 4, y = 0, z = 0.556 ± 5; HII(DII) in 3m: x = 0.675 ± 4, y = 0, z = 0.466 ± 5. The angle H-O -H (D-O-D) is 107.0° and the H-H distance is 1.603 + 3 Å. Including dynamical corrections, the equilibrium positions are: HI(DI) : x = 0.459 ± 4, y - 0, z = 0.550 ± 5; HII(DII): x = 0.669 ± 4, y = 0, z = 0.464 ± 5. The H-H distance is then 1.537 ± 5 Å. From the 2H-NMR the nuclear quadrupole coupling constant of the deuterons is at T = 22 °C: e2qQ/h = 132.0 ± 1.0 kHz; η = 0.754 ± 5. The major principal axis of the electric field gradient tensor is perpendicular to the twofold axis of the molecule D2O. At T = -25 °C for the two deuteron atoms of one molecule D2O, the values (e2qQ/h)I = 239.7 ± 1.0 kHz; ηI = 0.118 ± 2; (e2qQ/h)II = 235.9 ± 1.0 kHz; ηII = 0.125 ± 2 have been found. Here the intermediate principal axis of the FGT is perpendicular to the H-O-H plane. The direction cosines of the FGTs have been determined. The activation energy for the flipping process was found to be 12.7 kcal. mol-1. The possible hydrogen bonds O-H…Cl are discussed.

Studies of Successive Phase Transitions and Molecular Motions in [Mg(H2O)6][SiF6] by 1,2H and 19F NMR

1998 ◽  
Vol 53 (6-7) ◽  
pp. 453-458 ◽  
Author(s):  
Junko Kimura ◽  
Takeshi Fukase ◽  
Motohiro Mizuno ◽  
Masahiko Suhara
Keyword(s):  
Phase Transitions ◽  
Nmr Spectra ◽  
Quadrupole Coupling Constant ◽  
Coupling Constant ◽  
Molecular Motions ◽  
Exponential Factor ◽  
H Nmr ◽  
Quadrupole Coupling ◽  
Constant E ◽  
Successive Phase

Abstract The successive phase transitions of [Mg(H2O)6][SiF6] were studied by measuring 2H NMR spectra. The quadrupole coupling constant e2Qq/h and asymmetry parameter η changed drastically at each transition temperature. 1,2H and 19F NMR Tl were measured for this compound to study the relation between the molecular motions and the successive phase transitions. The activation energy Ea and the pre-exponential factor τ0 for the reorientation of [SiF6]2- were estimated as 28 kJmol-1 and 6.0 x 10-14 s, and those of the 180° flip of H2O as 33 kJmol-1 and 4.0x 10-14 s. These two motions occur rapidly even in phase V. For the reorientation of [Mg(H2O)6]2+ , Ea = 62 kJmol-1 and τ0 = 1.1 x 10-16 s were obtained from the simulation of 2H NMR spectra. The jump rate of this motion is of the order of 104 -106 s-1 in phase II. These results suggest that the successive phase transitions are closely related to the motion of [Mg(H2O)6]2+ .

Hydrogen Bond Studies

1977 ◽  
Vol 32 (2) ◽  
pp. 134-139 ◽  
Author(s):  
Bo Berglund ◽  
Jörgen Tegenfeldt
Keyword(s):  
Asymmetry Parameter ◽  
Room Temperature ◽  
Sodium Perchlorate ◽  
Quadrupole Coupling Constant ◽  
Water Molecules ◽  
Coupling Constant ◽  
Nmr Spectrum ◽  
Quadrupole Coupling ◽  
Constant E ◽  
The Difference

The quadrupole splittings in the deuterium NMR spectrum from single crystals of deuterated sodium Perchlorate monohydrate, NaClO4-D2O, have been measured at 25 °C and - 55 °C. At room temperature, the 180° flip frequency of the D2O molecules is large compared to the difference between the splittings for the two deuterons. The average quadrupole coupling constant (e2 q Q/h) and asymmetry parameter η are 134.1(4) kHz and 0.621(5), respectively. At -55 °C, the electric field gradient tensors for each of the two deuterons were observed corresponding to slowly flipping water molecules, and e2 qQ/h and η for the two deuterons are 231.5(6) and 226.7(6) kHz and 0.196(4) and 0.195(5), respectively. The results indicate that the hydrogen positions in NaClO4-H2O are dynamically disordered

scholarly journals Electric Quadrupole Interaction of 20F in a KZnF3 Single Crystal

1976 ◽  
Vol 31 (11) ◽  
pp. 1298-1302 ◽  
Author(s):  
H. Ackermann ◽  
D. Dubbers ◽  
M. Grupp ◽  
P. Heitjans ◽  
H.-J. Stöckmann ◽  
...  
Keyword(s):  
Single Crystal ◽  
Room Temperature ◽  
Electric Quadrupole ◽  
Quadrupole Coupling Constant ◽  
Electric Quadrupole Interaction ◽  
Coupling Constant ◽  
Nmr Spectrum ◽  
Quadrupole Coupling ◽  
Γ Ray ◽  
Anisotropy Measurement

Abstract Nuclear magnetic resonance measurements were carried out on neutron activated 20F(T1/2=11s) nuclei in a single crystal of KZnF3. The quadrupolar splitted NMR spectrum, detected via the 20F β-radiation asymmetry, could be observed using a radio frequency modulation technique. The quadrupole coupling constant was determined to e2 q Q/h= + (12.0 ± 1.5) MHz at room temperature. The sign of e2 q Q was obtained from a simultaneous γ-ray anisotropy measurement on the succeeding 20Ne transition. Utilising a calculated field gradient of the fluorine atom, an fQ = 4.6% is determined. This value is compared with literature data of similar compounds.

121Sb NMR and SCF-MS-Xα Studies of Quadrupole Interaction and The Electronic Structure of Mixed-Valence Compound, Cs2SbCl6

1996 ◽  
Vol 51 (5-6) ◽  
pp. 672-676 ◽  
Author(s):  
Takahiro Ueda ◽  
Nobuo Nakamura
Keyword(s):  
Electronic Structure ◽  
Charge Transfer ◽  
Ground State ◽  
Mixed Valence ◽  
Quadrupole Coupling Constant ◽  
Coupling Constant ◽  
Nmr Spectrum ◽  
Quadrupole Coupling ◽  
Mixed Valence Compound ◽  
Complex Anions

Cs2SbCl6 is known as a typical mixed-valence compound. It crystallizes into a tetragonal space group I41/amd and contains two different complex anions, Sb(III)Cl3-6 and Sb(V)Cl-6 . The dark blue color of this compound has been considered to originate from a charge transfer between the above two anions. In order to study the electronic structure of these complex anions and the existence of charge transfer between them we measured the 121Sb NMR spectrum and carried out molecular orbital calculations on the electronic states of these anions. The 121Sb NMR spectrum consists of two peaks at 0 and 30 kHz which can be assigned to the central transition of 121Sb in Sb(V)Cl-6 and Sb(III)Cl3-6 , respectively. The line shape analyses of the spectra led to nuclear quadrupole coupling constants of nearly zero for Sb(V)Cl-6 and 4.9 ± 0.5 MHz for Sb(III)Cl3-6 at room temperature. The quadrupole coupling constant of 121Sb(III) decreases steadily on heating. The calculations of the electronic ground state energies of both anions were calculated by the MS-Xα molecular orbital method. The calculated charge-transfer band from the A1g state of Sb(III)Cl3-6 to the A1g state of Sb(V)Cl-6 appears at 610 nm and can account for the experimental electronic spectrum, the calculated quadrupole coupling constant in Sb(III)Cl3-6 however is far larger than the experimental one. The contribution of the charge-transferred state to the ground state is negligible and so the temperature dependence of the quadrupole coupling constant of 121Sb(III) is attributed to an anisotropic thermal expansion of the compound.

ß-NMR Study of the Electric Field Gradient in the Metallic Intercalation Compound LiC6

1986 ◽  
Vol 41 (1-2) ◽  
pp. 109-112 ◽  
Author(s):  
P. Freiländer ◽  
P. Heitjans ◽  
H. Ackermann ◽  
B. Bader ◽  
G. Kiese ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Intercalation Compound ◽  
Quadrupole Coupling Constant ◽  
Layered Compound ◽  
Thermal Neutrons ◽  
Coupling Constant ◽  
Nmr Study ◽  
Nuclear Magnetic Resonance Spectra ◽  
Quadrupole Coupling ◽  
Constant E

In the layered compound LiC6polarized β-active 8Li probe nuclei were produced by captureof polarized thermal neutrons. Nuclear magnetic resonance spectra of 8Li were recorded via theβ-radiation asymmetry. The 8Li quadrupole coupling constant e2qQ/h , measured in the temperature range T = 5 . .. 500 K decreases with increasing 7 from 45.2(8) to 22.8(4) kHz.Anomalies in the overall temperature dependence are discussed in terms of phase transitionsproposed for LiC6.

scholarly journals 7Li Solid State NMR Study of a TMEDA Complex of Trimethylsilylcyclopentadienyllithium

1993 ◽  
Vol 48 (11) ◽  
pp. 1555-1557 ◽  
Author(s):  
Tanja Pietraß ◽  
Paul K. Burkert
Keyword(s):  
Solid State ◽  
Nmr Spectroscopy ◽  
Solid State Nmr ◽  
Quadrupole Coupling Constant ◽  
Structural Features ◽  
Coupling Constant ◽  
X Ray ◽  
Nmr Study ◽  
Quadrupole Coupling ◽  
Increasing Temperature

7Li solid state NMR spectroscopy of Ν,Ν,N′,N′-tetramethylethylenediamine-trimethylsilylcyclopentadienyllithium yielded an unusually large quadrupole coupling constant, that decreases with increasing temperature (188-165 kHz in the temperature range 210-335 K). Structural features, known from the X-ray analysis, are compared with the NMR results.

51V and 93Nb high resolution NMR study of NbVO5

1991 ◽  
Vol 6 (2) ◽  
pp. 393-400 ◽  
Author(s):  
J. Davis ◽  
D. Tinet ◽  
J.J. Fripiat ◽  
J.M. Amarilla ◽  
B. Casal ◽  
...  
Keyword(s):  
Chemical Shift ◽  
Chemical Shift Anisotropy ◽  
Quadrupole Coupling Constant ◽  
Isotropic Chemical Shift ◽  
Coupling Constant ◽  
Nmr Study ◽  
Resonance Frequencies ◽  
Quadrupole Coupling ◽  
High Resolution Nmr ◽  
Lower Electric Field

NbVO5 is characterized by 51V and 93Nb NMR resonance frequencies strongly upfield shifted when compared to those in model compounds V2O5 and LiNbO3. The chemical shift anisotropy dominates the 51V observed spectrum in a magnetic field of 11.7 T. The asymmetry parameter ηc is 0.2 and the quadrupole coupling constant is relatively small (1 MHz). The quadrupolar Hamiltonian overwhelmingly dominates the 93Nb spectrum (ηQ = 0.9) and the quadrupole coupling constant is huge (16.5 MHz). In agreement with the structure obtained from the x-ray powder diagram the isotropic chemical shift of 51V suggests that NbVO5 is indeed an orthovanadate. Interestingly, in NbVO5 the isotropic chemical shift of 93Nb reveals a better shielding of the 93Nb nucleus and a lower electric field gradient than in LiNbO3. Nb octahedra in NbVO5 are sharing corners whereas they share edges in LiNbO3.

Anomalous Temperature Dependence of the 99Tc Quadrupole Coupling and Disordering of Cesium Positions in CsTcO4

1992 ◽  
Vol 47 (1-2) ◽  
pp. 325-329 ◽  
Author(s):  
V. P. Tarasov ◽  
G. A. Kirakosyan ◽  
K. E. German
Keyword(s):  
Field Potential ◽  
Quadrupole Coupling Constant ◽  
Positive Temperature ◽  
Coupling Constant ◽  
Anomalous Temperature ◽  
First Order ◽  
Nmr Study ◽  
Principal Axes ◽  
Quadrupole Coupling ◽  
Population Ratio

AbstractA 99T c and 133Cs solid-state NMR study of polycrystalline CsTcO4 at a field of 7.04 T and temperatures from 90 to 430 K revealed first-order quadrupole effects. 99T c quadrupole coupling constant, Cq, shows anomalous positive temperature coefficients and decreases from 2.0 MHz at 430 K to 0.45 MHz at 90 K. The asymmetry parameter, η (99Tc) , is zero at 430 K and at 210 K. The high-temperature minimum of η is associated with a phase transition from orthorhombic to tetragonal and the second minimum reflects an orientational change of the principal axes qxx and qyy of the EFG-tensor. The 133Cs NMR spectra are characterised by a superposition of the two powder multiplets from the first-order couplings which arise from magnetically and crystallographically nonequivalent cesium sites, Cs (1) and Cs (2); the population ratio of Cs (2) and Cs (1), p2/p1 , varies from 2.0 at 120 K to 6.5 at 373 K. The nonequivalence and population changes are attributed to the temperature change of the crystal field potential in the vicinity of the cations.

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