SPIN–LATTICE RELAXATION EFFECTS OBSERVED IN THE CONTINUOUS POWER SATURATION OF PARAMAGNETIC LINES

1960 ◽  
Vol 38 (3) ◽  
pp. 495-503 ◽  
Author(s):  
G. V. Marr ◽  
Prem Swarup
Keyword(s):  
Transition Probability ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Pulse Technique ◽  
Effective Spin ◽  
Spin Lattice ◽  
Relaxation Effects ◽  
Continuous Power ◽  
Photon Interactions

The dependence of the conventional saturation parameter on the incident microwave power is considered for Lorentzian-shaped paramagnetic lines and applied to a study of the [Formula: see text] transitions of Cr+++ in K3Co(CN)6 and Gd+++ in La(C2H5SO4)3∙9H2O at 9 kMc/sec and 4.2 °K. It is shown that the experimental observations may be explained on the basis of a spin–lattice transition probability which depends on spin–photon interactions. Values of the effective spin–lattice relaxation times are compared with pulse technique determinations and estimates of the corresponding phonon relaxation times are also given.

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.

Molecular Motion in Solid Tetrabutylammonium Tetrafluoroborate

1991 ◽  
Vol 46 (6) ◽  
pp. 545-550 ◽  
Author(s):  
B. Szafranska ◽  
A. Kozak ◽  
Z. Pająk
Keyword(s):  
Relaxation Times ◽  
Activation Parameters ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Fluorine Nmr ◽  
Spin Lattice ◽  
Relaxation Effects ◽  
Second Moments ◽  
Wide Range ◽  
Tetrabutylammonium Tetrafluoroborate

Abstract Proton and fluorine NMR second moments and spin-lattice relaxation times for polycrystalline tetrabutylammonium tetrafluoroborate have been measured over a wide range of temperatures at several Larmor frequencies. An analysis of cross-relaxation effects results in a determination of activation parameters for anion and cation reorientations. Three solid phases characterized by different ion dynamics are evidence

Cation and Anion Reorientation at Phase Transition in Pyridinium Tetrafluoroborate

1990 ◽  
Vol 45 (1) ◽  
pp. 33-36 ◽  
Author(s):  
J. Wąsicki ◽  
Z. Pająk ◽  
A. Kozak
Keyword(s):  
Phase Transition ◽  
Relaxation Times ◽  
Activation Parameters ◽  
Lattice Relaxation ◽  
High Temperature Phase ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
Spin Lattice ◽  
Relaxation Effects ◽  
Temperature Dependences

AbstractTemperature dependences of 1H and 19F second moment and spin-lattice relaxation times for polycrystalline pyridinium tetrafluoroborate were measured. A phase transition was discovered at 202 K. A model of cation reorientation between inequivalent (low-temperature phase) and equivalent (high-temperature phase) equilibrium positions is proposed. Whether the anion reorients isotropically or about a symmetry axis cannot be decided. An analysis of cross-relaxation effects yielded activation parameters for cation and anion reorientation. The rotational correlation times for both ions converge just at the phase transition reaching the value of 10-10s.

scholarly journals FIELD DEPENDENCE OF SPIN-LATTICE RELAXATION TIMES OF Cr3+

1966 ◽  
Vol 44 (7) ◽  
pp. 1387-1399 ◽  
Author(s):  
N. Rumin
Keyword(s):  
Relaxation Time ◽  
Transition Probability ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Field Frequency ◽  
Effective Spin ◽  
Return To Equilibrium ◽  
Spin Lattice Relaxation Time ◽  
Spin Lattice

Relative changes in the effective, one-phonon, spin-lattice relaxation time with transition, magnitude, and direction of magnetic field, frequency, and temperature have been computed for Cr3+ in K3Co(CN)6, Al2O3, and RbAl(SO4)2∙12H2O from a simplified expression for the transition probability requiring knowledge of only the spin Hamiltonian for the particular salt. A comparison with published experimental data, augmented by measurements obtained as part of the present work, indicates that the changes are usually predicted to better than a factor of two.Calculations show that the pulse saturation, resonance-dispersion, and steady-state saturation techniques should yield the same effective spin-lattice relaxation time for an S > 1/2 spin system, when the return to equilibrium is characterized by a simple exponential.

Influence of cross-relaxation on NMR spin-lattice relaxation times

1973 ◽  
Vol 11 (2) ◽  
pp. 143-162 ◽  
Author(s):  
I.D Campbell ◽  
Ray Freeman
Keyword(s):  
Relaxation Times ◽  
Lattice Relaxation ◽  
Cross Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice

Tissue distribution and magnetic resonance spin lattice relaxation effects of gadolinium-DTPA.

Radiology ◽  
1985 ◽  
Vol 154 (3) ◽  
pp. 723-726 ◽  
Author(s):  
G Strich ◽  
P L Hagan ◽  
K H Gerber ◽  
R A Slutsky
Keyword(s):  
Magnetic Resonance ◽  
Tissue Distribution ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Gadolinium Dtpa ◽  
Spin Lattice ◽  
Relaxation Effects ◽  
Resonance Spin
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