Spin-lattice relaxation in solid and liquid CH4–Kr mixtures

1984 ◽  
Vol 62 (5) ◽  
pp. 431-434 ◽  
Author(s):  
P. Calvani ◽  
F. De Luca ◽  
B. Maraviglia
Keyword(s):  
Transition Temperature ◽  
Melting Point ◽  
Solid Phase ◽  
Molar Fraction ◽  
Lattice Relaxation ◽  
Intramolecular Interactions ◽  
Spin Lattice Relaxation ◽  
Solidus Curve ◽  
Spin Lattice ◽  
Dipolar Contribution

T1 has been measured at 4 MHz and 78 K < T < 120 K in mixtures having a Kr molar fraction c up to 0.8. The transition temperature Ts, corresponding to the solidus curve, has been determined for several values of c by observing the large discontinuity in T1 as in pure CH4. In the solid phase, the intermolecular dipolar contribution to the relaxation rate is found to be dominant at T > 80 K, and our data are in agreement with a simple model based on the Torrey–Sholl theory. Above the melting point, T1 becomes independent of c, thus suggesting that relaxation may be driven by intramolecular interactions in the liquid phase.

Barriers to rotation of the cyclopentadienyl ligand: spin-lattice relaxation time measurements and atom–atom potential calculations on cyclopentadienyl manganese and rhenium tricarbonyl and vanadium tetracarbonyl complexes

1983 ◽  
Vol 61 (4) ◽  
pp. 737-742 ◽  
Author(s):  
D. F. R. Gilson ◽  
G. Gomez ◽  
I. S. Butler ◽  
P. J. Fitzpatrick
Keyword(s):  
Relaxation Time ◽  
Molecular Conformation ◽  
Crystal Packing ◽  
Solid Phase ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Spin Lattice Relaxation Time ◽  
Spin Lattice ◽  
Atom Potential

The barriers to cyclopentadienyl ring rotation in the solid phase have been measured by spin-lattice relaxation time methods for the organometallic complexes CpMn(CO)3 (7.24 kJ mol−1), CpRe(CO)3 (7.15 kJ mol−1), and CpV(CO)4 (7.07 kJ mol−1), where Cp = η5-C5H5. Nonbonded atom–atom potential calculations of the barriers in these complexes and in BzCr(CO)3 (Bz = η6-C6H6) show that the molecular conformation of the Mn and Re compounds is determined by crystal packing forces and that concerted ring motions are possible for the cyclopentadienyl complexes, but not for the benzene chromium tricarbonyl.

Molecular Motion in Solid Tetraethyl -and Tetrapropylammonium Tetrafluoroborates

1995 ◽  
Vol 50 (6) ◽  
pp. 584-588 ◽  
Author(s):  
Barbara Szafrańska ◽  
Zdzisław Pająk
Keyword(s):  
Molecular Motion ◽  
Solid Phase ◽  
Complex Cation ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Fluorine Nmr ◽  
Spin Lattice ◽  
Second Moments ◽  
Wide Range

Abstract Proton and fluorine NMR second moments and spin-lattice relaxation times for polycrystalline tetraethyl-and tetrapropylammonium tetrafluoroborates have been measured over a wide range of temperatures. Solid-solid phase transitions were found for both compounds and confirmed by DSC. Methyl group C3 reorientation followed by more complex cation motions was evidenced in the low temperature phases. Overall cation reorientation characterises the high temperature phases of both compounds. Isotropic anion reorientation was found in both salts in both phases.

1H and 19F NMR Study of Cation and Anion Motions in Guanidinium Fluoroantimonates

1995 ◽  
Vol 50 (8) ◽  
pp. 742-748 ◽  
Author(s):  
M. Grottel ◽  
A. Kozak ◽  
Z. Pająk
Keyword(s):  
Solid Phase ◽  
Relaxation Times ◽  
Activation Parameters ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
Fluorine Nmr ◽  
Spin Lattice ◽  
Nmr Study ◽  
Guanidinium Cation

Abstract Proton and fluorine NMR linewidths, second moments, and spin-lattice relaxation times of polycrystalline [C(NH2)3]2SbF5 and C(NH2)3SbF6 were studied in a wide temperature range. For the pentafluoroantimonate, C3-reorientation of the guanidinium cation and C4-reorientation of the SbF5 anion were revealed and their activation parameters determined. The dynamical inequivalence of the two guanidinium cations was evidenced. For the hexafluoroantimonate, two solid-solid phase transitions were found. In the low temperature phase the guanidinium cation undergoes C3 reorien­ tation while the SbF6 anion reorients isotropically. The respective activation parameters were derived. At high temperatures new ionic plastic phases were evidenced.

1H and 19 F NMR Study of Cation and Anion Motions in Guanidinium Hexafluorozirconate

1996 ◽  
Vol 51 (9) ◽  
pp. 991-996 ◽  
Author(s):  
M. Grottel ◽  
A. Kozak ◽  
Z. Pająk
Keyword(s):  
Solid Phase ◽  
Relaxation Times ◽  
High Mobility ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Fluorine Nmr ◽  
Spin Lattice ◽  
Nmr Study ◽  
Wide Range ◽  
Deuterated Analogue

Abstract Proton and fluorine NMR second moments and spin-lattice relaxation times of polycrystalline guanidinium hexafluorozirconate and its deuterated analogue were studied in laboratory (60 MHz) and rotating (H1 = 20 G) frames over a wide range of temperature. An analysis of the experimental results enabled us to reveal a dynamical inequivalence of two crystallographically independent cations and an unexpected high mobility of nonspherical anion dimers. A comparison of the ions dynamics in 2:1 complex studied with the guanidinium 1:1 and 3:1 complexes has shown a significant contribution of the hydrogen bonds to the potential barriers hindering the anion reorientations. At low temperatures a proton motion in the hydrogen bond and at 400 K a solid-solid phase transition have been discerned.

A proton magnetic resonance relaxation study of molecular motions in trimethylamine-borane

1976 ◽  
Vol 54 (7) ◽  
pp. 1087-1091 ◽  
Author(s):  
T. T. Ang ◽  
B. A. Dunell
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Solid Phase ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Free Induction ◽  
Resonance Spin ◽  
Resonance Relaxation

Proton magnetic resonance spin–lattice relaxation times T1 have been measured for trimethylamine-borane from 120 to 380 K, a few degrees above the melting point. Minima in T1 at 157 and 259 K are attributed to threefold reorientation of each of the three methyl groups and the borane group and to threefold reorientation of the whole molecule about the B—N axis, respectively. Activation energies for these processes were found to be 3.3 and 6.7 kcal/mol. Abrupt changes in T1 at 350 and 360 K correspond exactly with heat capacity transitions observed by other workers. The time constant for the decay of the free induction signal (FID curve) changes by two orders of magnitude at 360 K. Having a value of some 3 ms above 360 K, it shows that there must be rapid diffusion as well as molecular tumbling in the highest temperature solid phase.

Molecular Motion in Solid Tetrapropylammonium Bromide and Iodide

1992 ◽  
Vol 47 (11) ◽  
pp. 1115-1118 ◽  
Author(s):  
S. Lewicki ◽  
B. Szafranska ◽  
Z. Pajak
Keyword(s):  
Molecular Motion ◽  
Solid Phase ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Methyl Groups ◽  
Methyl Group ◽  
Spin Lattice ◽  
Tetrapropylammonium Bromide ◽  
Solid Phase Transition

Abstract The proton NMR second moment and spin-lattice relaxation time for tetrapropylammonium bromide and iodide have been measured over a wide temperature range. A solid-solid phase transition related to the onset of cation tumbling was found for both salts and confirmed by DTA. In the low temperature phases methyl group reorientation was evidenced. For iodide a dynamic nonequivalence of the methyl groups and the onset of ethyl groups motion was also discovered

Protonenresonanzuntersuchungen über innermolekulare Bewegungen, Phasenumwandlungen und Entglasungsvorgänge in festen Äthern

1966 ◽  
Vol 21 (8) ◽  
pp. 1231-1240 ◽  
Author(s):  
K. Grude ◽  
J. Haupt ◽  
W. Müller-Warmuth
Keyword(s):  
Solid State ◽  
Melting Point ◽  
Lattice Relaxation ◽  
Relaxation Mechanism ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Small Range ◽  
Second Moment ◽  
Spin Lattice ◽  
Line Shapes

Proton magnetic resonance investigations on solid dimethylether (DM) , diethylether (DE) , dipropylether (DP), diisopropylether (DIP), dibutylether (DB), dimethoxymethane (DMM), diethoxymethane (DEM), dimethoxyethane (DME), diethoxyethane (DEE), acetaldehyde (ACA) and diethylketone (DEK) yielded information on molecular motion, solid state phase transitions and deglassing processes. The temperature-dependence of the spin-lattice relaxation time and the second moment was studied between the melting point and 77 °K using radiofrequency pulse techniques. Both spin-lattice relaxation and line shapes are governed by dipolar interactions which are modulated in time by hindered rotations of CH3-groups. The parameters for this relaxation mechanism are given in detail. Concerning the general results it was possible to distinguish between three cases : a) substances that form only one crystalline phase in the solid state (DM, DIP, DEM, DME, ACA, and DEK); b) ethers that form only a vitreous state (DP and DEE) and c) ethers that form both crystalline and vitreous states depending on the way in which the liquid was cooled. In the last case a pronounced decrease of the second moment of the absorption line was observed near the phase transition from the vitreous to the polycrystalline state. This means that within a small range of temperatures far below the melting point some kind of melting of the glass occurs before the crystal is formed.

Proton spin-lattice relaxation in some amino acids in the solid phase

1971 ◽  
Vol 5 (2) ◽  
pp. 262-266
Author(s):  
R.G.C McElroy ◽  
Ronald Y Dong ◽  
M.M Pintar ◽  
W.F Forbes
Keyword(s):  
Amino Acids ◽  
Solid Phase ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Spin Lattice
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