Étude du mouvement des ions dans les fluosilicates par RMN

Dereppe, Jean-Marie; Lobo, Pedro W.; Meerssche, M. Van

doi:10.1051/jcp/1964611076

Cited by 18 publications

(10 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Afin de compléter la bibliographie concernant le fluosilicate de fer pur ou dilué dans le fluosilicate de zinc, signalons l'existence d'études de R.M.N. réalisées, soit sur monocristal de fluosilicate ferreux à 4,2 K j15], qui montrent que la symétrie de l'octaèdre [Fe(H20)6]2+ y est plus basse que trigonale, soit sur diverses poudres, à plus haute température [16], , qui mettent en évidence des mouvements rapides des protons et des ions fluor. L'influence de ces mouvements sur les spectres Môssbauer sera discutée dans la présente étude.…”

unclassified

Étude Mössbauer des propriétés électroniques, magnétiques et hyperfines de Fe2+ dans les fluosilicates

Varret

Jéhanno

1975

J. Phys. France

View full text Add to dashboard Cite

Nous interprétons ici la variation thermique de l'interaction quadrupolaire de Fe2+ dans les fluosilicates de Mg, Mn, Fe, Co, Ni, Zn, ainsi que la valeur du champ hyperfin observé dans des monocristaux de fluosilicate de fer pur ou de fer dilué dans le fluosilicate de zinc, soumis à des champs magnétiques extérieurs, dans diverses conditions d'orientation et de température. Compte tenu de données antérieures obtenues par des expériences en champ pulsé, nous obtenons, à basse température, dans un modèle de champ cristallin, les résultats suivants : — Dans le fluosilicate de zinc : δ/λ = séparation orbitale trigonale/couplage spin-orbite = 2,1 ± 0,1; λ = - 88 ± 3 cm-1; 3d = 3,7 ± 0,3 U.A. ; HF (terme de Fermi) = - 535 ± 30 kOe. — Dans le fluosilicate de fer : δ/λ ≃ 15, λ = - 100 ± 7 cm-1 et 3d = 4,0 ± 0,3 U.A. si l'on prend HF = — 535 kOe. De plus, l'anisotropie magnétique hyperfine observée dans le plan de facile aimantation ainsi que la valeur du paramètre d'asymétrie η = 0,32 ± 0,02 s'expliquent par l'introduction d'un potentiel cristallin supplémentaire, qui abaisse la symétrie et qu'il a fallu développer jusqu'à l'ordre 4

show abstract

unclassified

Étude Mössbauer des propriétés électroniques, magnétiques et hyperfines de Fe2+ dans les fluosilicates

Varret

Jéhanno

1975

J. Phys. France

View full text Add to dashboard Cite

show abstract

“…By fitting (9) to the temperature dependence of k, ko = 3.Ox 10 15 s~' and E a = 62 kJmol" 1 were obtained. Figure 5 shows the temperature dependences of 2 H and 19 F TI in [Mg(D 2 0) 6 ][SiF 6 ] (denoted as T ]D and Tip).…”

Section: H Nmr Spectramentioning

confidence: 99%

“…The determined parameters are given in Table 2. Here, TOH was estimated by using CHH = 19 G 2 , which was obtained from the experimental result of the second moment reduction AM 2 [9], using the relation C = (2/3)AM 2 .…”

Section: H 19 F T\ In[mg(d 0) 6 ][Sif 6 ]mentioning

confidence: 99%

“…The modulated structure in phase II has been studied by use of ESR spectroscopy, and a drastic change in the modulation amplitude at 343 K has been reported [2][3][4], Although the investigations have been performed with the diffraction methods, a detailed analysis of the modulated structure in the incommensurate phase has not been done [5][6][7][8]. These phase transitions can be considered to be related to the motions of H 2 0, [Mg(H 2 0) 6 [2,9,10]. Because of the cross relaxation between 1 H and l9 F, information about the motion of H 2 0 has not been obtained from 1 H NMR.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

Kimura

Fukase

Mizuno

et al. 1998

Zeitschrift Für Naturforschung A

View full text Add to dashboard Cite

The successive phase transitions of [Mg(H?0)6][SiF6] were studied by measuring 2 H NMR spectra. The quadrupole coupling constant e 2 Qq/h and asymmetry parameter 77 changed drastically at each transition temperature. 12 H and 19 F NMR T\ were measured for this compound to study the relation between the molecular motions and the successive phase transitions. The activation energy E a and the pre-exponential factor TO for the reorientation of [SiFö] 2~ were estimated as 28 kJmol" 1 and 6.0x 10~1 4 s, and those of the 180° flip of H 2 0 as 33 kJmol -1 and 4.0x 10" 14 s. These two motions occur rapidly even in phase V. For the reorientation of [Mg(H20)6] 2+ , E a = 62 kJmol -1 and TO = 1.1 x 10 -16 s were obtained from the simulation of : H NMR spectra. The jump rate of this motion is of the order of 10 4 -10 6 s _I in phase II. These results suggest that the successive phase transitions are closely related to the motion of [Mg(H 2 0) 6 ] 2+ .

show abstract

“…3 They observed that abrupt reductions in the second moments occurred at 200 and 300 o K. These results imply2 that the rotational correlation times Tc~1O-5 sec for the SiFs2-near 200 0 K and likewise for the Mg(H20)s2+ ions near 300 o K. Since the molecular motions are most efficient for relaxation when wTc~l (where w is the NMR angular frequency), it follows that the rotations of the Mg(H 2 0)s2+ ions will be too slow for effective spin-lattice relaxation over most of the experimental temperature range.…”

mentioning

confidence: 99%

Coupled Nuclear Spin Relaxation and Internal Rotations in Magnesium Fluosilicate Hexahydrate

Utton

Tsang

1972

The Journal of Chemical Physics

View full text Add to dashboard Cite

Both proton and fluorine nuclear spin—lattice relaxations have been studied by the 180°-90° pulse method in MgSiF6 · 6 H2O at 25 and 13 MHz over the temperature range 170–350°K. Nonexponential behaviors have been observed. Both 1H and 19F relaxations may be characterized by the same pair of relaxation times, the shorter component due to the intermolecular H–F dipolar interaction. The results indicate that the SiF62− ions are reorienting with an activation energy, V = 31 ± 4 kJ/mole = 7.5 ± 1.0 kcal/mole, and a frequency factor τ0 = 10−14 ± 1sec. These values are consistent with other hydrogen-bonded fluorine compounds.

show abstract

Étude du mouvement des ions dans les fluosilicates par RMN

Cited by 18 publications

References 0 publications

Étude Mössbauer des propriétés électroniques, magnétiques et hyperfines de Fe2+ dans les fluosilicates

Étude Mössbauer des propriétés électroniques, magnétiques et hyperfines de Fe2+ dans les fluosilicates

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

Coupled Nuclear Spin Relaxation and Internal Rotations in Magnesium Fluosilicate Hexahydrate

Contact Info

Product

Resources

About

Étude du mouvement des ions dans les fluosilicates par RMN

Cited by 18 publications

References 0 publications

Étude Mössbauer des propriétés électroniques, magnétiques et hyperfines de Fe2+ dans les fluosilicates

Étude Mössbauer des propriétés électroniques, magnétiques et hyperfines de Fe2+ dans les fluosilicates

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

Coupled Nuclear Spin Relaxation and Internal Rotations in Magnesium Fluosilicate Hexahydrate

Contact Info

Product

Resources

About

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