A Nuclear Spin Relaxation Study of the Spin–Rotation Interaction in Spherical Top Molecules

1972 ◽  
Vol 50 (12) ◽  
pp. 1252-1261 ◽  
Author(s):  
James A. Courtney ◽  
Robin L. Armstrong
Keyword(s):  
Lattice Relaxation ◽  
Relaxation Mechanism ◽  
Lattice Relaxation Time ◽  
Spin Rotation ◽  
Spin Lattice Relaxation ◽  
Molecular Reorientation ◽  
Effective Spin ◽  
Spin Lattice ◽  
Pass Through ◽  
Rotation Constant

The spin–lattice relaxation time T1 of the 19F nuclei was measured in gaseous samples of CF4, SiF4, GeF4, and SF6 at room temperature for densities from 0.015 to 20 amagat. In each case T1 was observed to pass through a minimum for some density less than 0.50 amagat. In addition, T1 was measured in the extreme narrowing region for SF6 at 238, 265, 293, 313, and 349.5 K.. The spin–rotation interaction provides the dominant relaxation mechanism in all cases. The data are analyzed on the basis of the assumption that the collision modulated spin–rotation interaction may be described by a single correlation function which is a simple exponential function of time. Values of an effective spin–rotation constant and a cross section for molecular reorientation are obtained for each gas. Assuming the validity of the model used to analyze the relaxation data, the combination of nuclear magnetic relaxation results with molecular beam measurements yields more accurate values of the anisotropic spin–rotation constant Cd than have been previously available.

A Nuclear Spin Relaxation Study of the Spin–Rotation Interaction in Symmetric Top Molecules

1972 ◽  
Vol 50 (12) ◽  
pp. 1262-1272 ◽  
Author(s):  
Robin L. Armstrong ◽  
James A. Courtney
Keyword(s):  
Relaxation Times ◽  
Lattice Relaxation ◽  
Relaxation Mechanism ◽  
Spin Rotation ◽  
Spin Lattice Relaxation ◽  
Molecular Reorientation ◽  
Effective Spin ◽  
Spin Lattice ◽  
Simple Exponential Function ◽  
Symmetric Top Molecules

The spin–lattice relaxation times T1 of 1H, 19F, and 31P nuclei were measured in gaseous samples of BF3, CHF3, CH3F, PH3, and NH3 at room temperature for densities from 0.03 to 10 amagat. In several cases the behavior of T1 at the lowest densities snowed deviations from the linear variation characteristic of the extreme narrowing region. The spin–rotation interaction provides the dominant relaxation mechanism in all cases. The data are analyzed on the basis of the assumption that the collision modulated spin–rotation interaction may be described by a single correlation function which is a simple exponential function of time. Values of an effective spin–rotation constant and a cross section for molecular reorientation are obtained for each gas. The results obtained are compared with those available from other types of experiments. This comparison indicates that the theory for spin–lattice relaxation in dilute gases of symmetric top molecules needs to be carefully reassessed.

scholarly journals Observation of the Influence of Centrifugal Distortion of the Methane Molecule on Nuclear Spin Relaxation in the Gas

1972 ◽  
Vol 50 (3) ◽  
pp. 251-258 ◽  
Author(s):  
P. A. Beckmann ◽  
M. Bloom ◽  
E. E. Burnell
Keyword(s):  
Larmor Frequency ◽  
Lattice Relaxation ◽  
Relaxation Mechanism ◽  
Lattice Relaxation Time ◽  
Spin Rotation ◽  
Spin Lattice Relaxation ◽  
Centrifugal Distortion ◽  
Rotational States ◽  
Spin Lattice ◽  
Pass Through

The spin–lattice relaxation time T1 was measured in gaseous CH4 as a function of density at room temperature between 0.006 and 7.0 amagats. T1 was found to pass through a minimum near 0.04 amagats in agreement with previous, less precise measurements. The spin–rotation interaction is the dominant relaxation mechanism in gaseous CH4. Since the spin–rotation constants are accurately known for CH4, the relaxation experiments provide a check on the theory of spin–lattice relaxation for spherical top molecules. In the conventional theory, it is assumed that the correlation function of the spin–rotation interaction is a simple exponential function of time. These experiments show that this assumption is not true for CH4 gas. The observed fine structure in the plot of relaxation rate versus density is attributed to the influence of centrifugal distortion of the CH4 molecule, which removes the degeneracy of rotational states having the same value of the quantum number J by an amount somewhat greater than the nuclear Larmor frequency of 30 MHz.

scholarly journals Spin-Gitter-Relaxationszeit T1 von Nitrilkohlenstoffen / Spin-Lattice-Relaxation Time T1 of Nitrile Carbon-atoms

1979 ◽  
Vol 34 (3) ◽  
pp. 375-379 ◽  
Author(s):  
H. Sterk ◽  
J. Kalcher ◽  
G. Kollenz ◽  
H. Waldenberger
Keyword(s):  
Relaxation Time ◽  
Correlation Time ◽  
Lattice Relaxation ◽  
Relaxation Mechanism ◽  
Lattice Relaxation Time ◽  
Spin Rotation ◽  
Spin Lattice Relaxation ◽  
Hydrogen Atoms ◽  
Spin Lattice ◽  
Almost All

Abstract It is shown that in almost all nitrile carbon-atoms T1 depends first of all on the inter-and/or intramolecular dipol-dipol-relaxation mechanism. Only acetonitrile, as is already known, shows a remarkable dependence on the spin-rotation-relaxation mechanism. This influence is strongly decreasing with an increasing number of atoms, specially hydrogen atoms, in the molecule. The significance of the correlation time r is discussed extensively and the experimental results are verified by calculation of T1 using the viscosity and the inertial moments as parameters.

A nuclear magnetic resonance investigation of solid tetraphosphorus trisulphide

1978 ◽  
Vol 364 (1719) ◽  
pp. 553-567 ◽  
Keyword(s):  
Phase 1 ◽  
Lattice Relaxation ◽  
Relaxation Mechanism ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Minor Role ◽  
High Resolution Spectrum ◽  
Basal Nuclei ◽  
Spin Lattice ◽  
A Minor

The 31 P n. m. r. spectrum and spin–lattice relaxation time in polycrystalline P 4 S 3 have been measured between 77 and 500 K in the range 7 to 25 MHz. In phase II the 31 P n. m. r. spectra and second moments are dominated by the anisotropic chemical shift interactions. Close to the first-order phase transition at 314 K the spectra are narrowed by reorientation of the molecules about their triad axes. This motion also generates anisotropicshift spin-lattice relaxation notable for its absence of frequency dependence. The activation energy of this motion was found to be 34 kJ mol -1 . Nuclear dipolar interactions play only a minor role. In phase 1 the molecules exhibit rapid quasi-isotropic reorientation and diffusion. The anisotropic broadening interactions are averaged out and an AB 3 high-resolution spectrum of a doublet and quartet are resolved at 420 K, well below the melting point, 446 K. In this phase the spin–rotation interaction relaxation mechanism becomes dominant. Taking advantage of the remarkable motional narrowing in this compound we report the first solid-state n. m. r. J spectrum. This spectrum, recorded at 410 K, allowed the J coupling between apical and basal nuclei in solid P 4 S 3 to be measured accurately, 70.4 ± 0.5 Hz.

1HNMR Study on the Motion of NH4+ in Ferroelectric NH4H(ClH2CCOO)2 and Mixed (NH4)1-xRbxH(ClH2CCOO)2 (x = 0.15)

2002 ◽  
Vol 57 (11) ◽  
pp. 883-887 ◽  
Author(s):  
M. Zdanowska-Fra̡czek ◽  
A. Kozaka ◽  
R. Jakubasb ◽  
J. Wa̡sickia ◽  
R. Utrechta
Keyword(s):  
Relaxation Time ◽  
Group Dynamics ◽  
Nmr Relaxation ◽  
Activation Parameters ◽  
Lattice Relaxation ◽  
Relaxation Mechanism ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Temperature Dependent ◽  
Spin Lattice

Temperature-dependent proton NMR relaxation time measurements have been performed at 60 MHz in order to study the NH4+ dynamics in ferroelectric NH4H(ClH2CCOO)2 and mixed Rbx(NH4)1-x(ClH2CCOO)2, where x = 0.15. The data indicate that the dominant relaxation mechanism for the NMR spin-lattice relaxation time T 1 in both crystals involves simultaneous NH4 group reorientation about their C2 and C3 symmetry axis in the paraelectric phase. Details of the NH4+reorientation have been inferred from analysis of temperature dependence of T1 assuming the Watton model. The activation parameters of the motionshave been determined.It has been found that the substitution of Rb does not change the activation parameters of the NH4 group dynamics.

Chlorine Nuclear Quadrupole Relaxation due to the Motion of Pyridinium Cations in Pyridinium Hexachlorometallates(IV): (pyH)2 MCl6 (M = Sn, Pb, Te)

1990 ◽  
Vol 45 (3-4) ◽  
pp. 477-480 ◽  
Author(s):  
Yutaka Tai ◽  
Tetsuo Asaji ◽  
Daiyu Nakamura
Keyword(s):  
Lattice Relaxation ◽  
Relaxation Mechanism ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Reorientational Motion ◽  
Quadrupole Relaxation ◽  
Potential Wells ◽  
Spin Lattice ◽  
Pyridinium Cations ◽  
Nuclear Quadrupole Relaxation

Abstract The temperature dependence of the chlorine quadrupole spin-lattice relaxation time T1Q was observed for one of the three 35Cl NQR lines of (pyH)2 MCl6(M = Sn, Pb, Te). Each T1Q curve can be devided into three temperature regions. In the low-and high-temperature regions, T1Q is dominantly determined by the relaxation mechanism due to the libration and reorientation of [MCl6]2- , respectively. In the intermediate temperature region, T1Q results from the modulation of the electric field gradient by the motion of the neighboring pyridinium cations. This way the reorientational motion of the cation between potential wells with nonequivalent depths is precisely characterized.

Spin–lattice relaxation of 1,2-dichloroethane in different solvents

1969 ◽  
Vol 47 (24) ◽  
pp. 4635-4638 ◽  
Author(s):  
E. Bock ◽  
E. Tomchuk
Keyword(s):  
Relaxation Rate ◽  
Lattice Relaxation ◽  
Relaxation Mechanism ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Weakly Magnetic ◽  
Solvent Molecules ◽  
The Individual ◽  
Deuterated Benzene

The spin–lattice relaxation time of the 1,2-dichloroethane molecule has been determined in 6 different nonmagnetic or weakly magnetic solvents at 20 °C, viz: deuterated benzene, carbon disulfide, deuterated 1,2-dichloroethane, carbon tetrachloride, and deuterated chloroform. From the experimental results the relaxation rate in infinitely dilute solution, the so called intramolecular relaxation rate, was determined for each solvent. It was found that the observed intramolecular relaxation rate could be successfully interpreted as arising solely from a dipole–dipole relaxation mechanism. It was further found that the individual differences in the value of the intramolecular spin–lattice relaxation rate of the 1,2-dichloroethane molecule in different solvents could be accounted for in terms of weak complex formation between the solute and solvent molecules.

MOLECULAR REORIENTATION IN FERROELECTRIC LITHIUM HYDRAZINIUM SULPHATE

1967 ◽  
Vol 45 (10) ◽  
pp. 3257-3263 ◽  
Author(s):  
W. D. MacClement ◽  
M. Pintar ◽  
H. E. Petch
Keyword(s):  
Low Temperatures ◽  
Room Temperature ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Resonance Absorption ◽  
Spin Lattice Relaxation ◽  
Kcal Mole ◽  
Molecular Reorientation ◽  
Hindered Rotation ◽  
Spin Lattice

The temperature dependence of the spin-lattice relaxation time T1 and of the second moment of the magnetic-resonance absorption signal has been determined for protons in powdered lithium hydrazinium sulphate over the range 80–480 °K. These measurements indicate that the hydrazinium ion is rigid only at very low temperatures. As the temperature is raised, the −NH3 group begins to undergo hindered rotation about the N–N axis with an activation energy of 4.2 kcal/mole and the effect of this motion on the line width becomes pronounced in the region of 85 °K. Further molecular reorientation begins above room temperature and is probably reorientation of the −NH2 group about either the N–N axis or the bisectrix of the H–N–H angle. Above 435 °K the hydrazinium ion begins to tumble about several axes and at 480 °K diffuses through the structure.

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.

Chlorine Nuclear Spin-Spin Relaxation Mechanism in Mg(H2O)6SnCl6 as Studied by NQR and NMR Techniques

1992 ◽  
Vol 47 (1-2) ◽  
pp. 277-282 ◽  
Author(s):  
Keizo Horiuchi ◽  
Daiyu Nakamura
Keyword(s):  
Relaxation Time ◽  
Spin Relaxation ◽  
Lattice Relaxation ◽  
Relaxation Mechanism ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Local Magnetic Field ◽  
Spin Lattice Relaxation Time ◽  
Spin Lattice ◽  
Increasing Temperature

AbstractThe 35Cl NQR spin-lattice relaxation time T1Q, spin-spin-relaxation time T2Q, and 1H NMR spin-lattice relaxation time in the rotating frame T1Q in Mg(H2O) 6SnCl6 were measured as functions of temperature. Above room temperature T2Q increased rapidly with increasing temperature, which can be explained by fluctuations of the local magnetic field at the chlorine nuclei due to cationic motions. From the T1Q experiments, these motions are found to be attributable to uniaxial and overall reorientations of [Mg(H2O)6 ] 2 + ions with activation energies of 95 and 116 kJ mol - 1 , respectively. Above ca. 350 K, T1Q decreased rapidly with increasing temperature, which indicates a reorientational motion of [SnCl6] 2 - ions with an activation energy of 115 kJ mol -1 .

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