Application of a pseudo-one-dimensional kinetic Ising model to proton spin-lattice relaxation rates in squaric acid (H2C4O4)

1985 ◽  
Vol 31 (5) ◽  
pp. 3059-3063 ◽  
Author(s):  
U. Deininghaus ◽  
H. Fischer ◽  
P. K. Kahol ◽  
M. Mehring
Keyword(s):  
Ising Model ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Squaric Acid ◽  
Relaxation Rates ◽  
Kinetic Ising Model ◽  
One Dimensional ◽  
Spin Lattice

An experimental evaluation of simplified procedures for determining the proton spin–lattice relaxation rates of natural products

1980 ◽  
Vol 58 (19) ◽  
pp. 2016-2023 ◽  
Author(s):  
Lawrence D. Colebrook ◽  
Laurance D. Hall
Keyword(s):  
Natural Products ◽  
Lattice Relaxation ◽  
Null Point ◽  
Proton Spin ◽  
Computational Method ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Spin Lattice ◽  
Simplified Procedures

A general discussion is given of the determination of the proton spin–lattice relaxation rates of natural products, with particular emphasis on use of the null-point method which, for the systems studied here, gives identical results with those obtained via the conventional (and relatively time consuming) computational method.

scholarly journals NMR Spin-Lattice Relaxation and Tunnelling of Partially Deuterated Methyl Groups

1991 ◽  
Vol 46 (12) ◽  
pp. 1123-1130 ◽  
Author(s):  
H. Langen ◽  
W. Müller-Warmuth
Keyword(s):  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Spin States ◽  
Relaxation Rates ◽  
Spin Lattice ◽  
Conversion Rates ◽  
Temperature Relaxation ◽  
Field Cycling ◽  
Additional Influence

Abstract Proton spin lattice relaxation rates have been measured at 15 and 30 MHz and down to 5 K for the partially deuterated molecular crystals 4-F-toluene, 4-Cl-toluene, and 2,6-Cl2-toluene. The behaviour of these materials is governed by methyl group tunnelling. As compared with the undeuterated compounds, the low temperature relaxation is enhanced and the details depend on the removal of the symmetry coupling between rotator and spin states. The hindering barriers remain unchanged, the A to E conversion rates are faster, and relaxation is dominated by spectral density contributions J(2ωo) and J(2ω0). In one case an additional influence of level-crossing energy transfer on relaxation is observed. Field-cycling spectroscopy reveals steps rather than peaks if the proton spin Zeeman and tunnelling splittings match

An experimental evaluation of nonselective proton spin–lattice relaxation rates: analyses of data for the eight isomeric 2,3,4-tri-O-acetyl-1,6-anhydro-β-D-hexopyranoses

1980 ◽  
Vol 58 (18) ◽  
pp. 1916-1922 ◽  
Author(s):  
Klaus Bock ◽  
Laurance D. Hall ◽  
Christian Pedersen
Keyword(s):  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Proton Relaxation ◽  
Relaxation Rates ◽  
Pyranose Ring ◽  
Solvent Concentration ◽  
Relaxation Data ◽  
Spin Lattice ◽  
Single Set

The nonselective spin–lattice relaxation rates (R1-values) have been determined for all of the ring protons of the eight isomers of 2,3,4-tri-O-acetyl-1,6-anhydro-(β-D-hexopyranose as 0.1 molar solutions in benzene-d6. The effects on the proton R1-values of changes in solvent, concentration, temperature, and proton impurities are documented and 13C R1-values are given to show that the first two sets of variations are due to changes in motional correlation times of the molecules. The proton relaxation data can be fitted by regressional analyses to a single set of interproton relaxation contributions, the numerical values of which accord with a 1C4 conformation for the pyranose ring somewhat distorted by the 1,6-anhydro bridge.

Proton Relaxation in Various Copper (II) Complexes and Determination of the Singlet-Triplet Separation

1980 ◽  
Vol 35 (1) ◽  
pp. 92-97 ◽  
Author(s):  
H. D. Jannek ◽  
W. Midler-Warmuth
Keyword(s):  
Copper Complexes ◽  
Lattice Relaxation ◽  
Magnetic Behaviour ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Proton Relaxation ◽  
Relaxation Rates ◽  
Temperature Dependent ◽  
Spin Lattice

Abstract Proton spin-lattice relaxation rates have been measured at 30 MHz as a function of temperature for a large number of dimeric copper complexes with the ligands 8-hydroxyquinoline, pyridine-N-oxide, methyl and dimethyl pyridine-N-oxide, and quinoline-N-oxide. Two carboxylates and adducts of several complexes with various solvents have also been studied. In contrast to some compounds with a normal magnetic behaviour, for most complexes a temperature dependent relaxation has been observed which agrees well with the concept of a weak antiferromagnetic interaction between the two Cu2+ ions. The singlet-triplet separations or exchange integrals have been determined.

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