Intermolecular potentials from NMR data: H2–N2O and H2–CO2

1983 ◽  
Vol 61 (5) ◽  
pp. 664-670 ◽  
Author(s):  
Lakshman Pandey ◽  
C. P. K. Reddy ◽  
K. Lalita Sarkar
Keyword(s):  
Relaxation Times ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Intermolecular Potential ◽  
Quadrupole Moments ◽  
Spin Lattice ◽  
Lennard Jones ◽  
Nmr Data ◽  
Potential Parameters

Proton spin-lattice relaxation times T1 were measured in mixtures of H2 with N2O as a function of density, composition, and temperature (200–400 K) in the region where [Formula: see text]. These data, along with the data obtained by Lalita and Bloom for H2–CO2, were interpreted, using Bloom–Oppenheim theory, to obtain the anisotropic intermoleeular potential parameters. Two models, (i) the Lennard–Jones (12–6) potential (LJP) and (ii) the modified Buckingham (exp-6) potential (MBP), were used to represent the isotropic part of the intermolecular potential. The relative anisotropy in the attractive r−6 term and the quadrupole moments of N2O and CO2 as obtained from MBP model are in better agreement with the values obtained from the polarizability data and the reported values, respectively, than those obtained from the LJP model.

Intermolecular potentials from proton spin–lattice relaxation time in H2–Ar and H2–N2 gas mixtures

1981 ◽  
Vol 59 (9) ◽  
pp. 1260-1266
Author(s):  
Lakshman Pandey ◽  
K. Lalita Sarkar
Keyword(s):  
Spin Echo ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Gas Mixtures ◽  
Lattice Relaxation Time ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Intermolecular Potential ◽  
Intermolecular Potentials ◽  
Spin Lattice

Proton spin-lattice relaxation times, T1, have been measured in H2–Ar and H2–N2 gas mixtures as a function of density (10 < ρ < 70 amagat), composition (~ 18–65%), and temperature (300–600 K) with a 30 MHz spin-echo spectrometer using phase sensitive detection. These data together with the T1 data obtained by Foster and Rugheimer and by Williams in these mixtures below 300 K have been analysed using the Bloom–Oppenheim theory. Models for intermolecular potentials to explain the T1 data have been proposed. It is found that the relative anisotropy in the attractive part of the intermolecular potential which fits the T1 data best compares well with that evaluated using polarizability data.

Intermolecular Potentials from NMR Data: I. CH4–N2 and CH4–CO2

1975 ◽  
Vol 53 (17) ◽  
pp. 1624-1630 ◽  
Author(s):  
S. Rajan ◽  
K. Lalita ◽  
S. V. Babu
Keyword(s):  
Relaxation Times ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Average Lifetime ◽  
Quadrupole Moments ◽  
Gaseous Mixtures ◽  
Spin Lattice ◽  
Least Squares Fit ◽  
The Given

Proton spin–lattice relaxation times have been measured in the gaseous mixtures CH4–N2 and CH4–CO2 as a function of density and composition in the temperature region 300–600 K. The values of T1/ρ extrapolated to 100% N2 and CO2 respectively were found to be proportional to T−n where n = 0.87 ± 0.14 for CH4–N2 and n = 0.91 ± 0.10 for CH4–CO2. It is not possible to fit these data using a hard sphere potential for the isotropic part. Using the Bloom–Oppenheim theory and assuming that the correlation time of the spin–rotation interaction can be approximated by the average lifetime of a molecule in the given J state, it is shown that the above temperature dependence can be fitted by a 12–6 Lennard–Jones potential combined with an appropriate anisotropic potential. We have obtained the strengths of the repulsive and attractive terms in the anisotropic potential by a least squares fit of the data. Using the known values of the quadrupole moments of N2 and CO2, the octopole moment of CH4 has been obtained.

PROTON SPIN-LATTICE RELAXATION TIMES OF HUMIC ACIDS AS DETERMINED BY SOLUTION NMR

Soil Science ◽  
2003 ◽  
Vol 168 (2) ◽  
pp. 128-136 ◽  
Author(s):  
Kaijun Wang ◽  
L. Charles Dickinson ◽  
Elham A. Ghabbour ◽  
Geoffrey Davies ◽  
Baoshan Xing
Keyword(s):  
Humic Acids ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Solution Nmr ◽  
Spin Lattice

Histopathological Evidence in Support of the Association of Elevated Proton Spin-lattice Relaxation Times with the Malignant State

1979 ◽  
Vol 65 (2) ◽  
pp. 157-162 ◽  
Author(s):  
S. S. Ranade ◽  
Smita Shah ◽  
G. V. Talwalkar
Keyword(s):  
Human Cancer ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Malignant Cell ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Histopathological Study ◽  
Spin Lattice ◽  
Malignant State ◽  
T Values

The pulsed nuclear magnetic resonance technique was explored for its potential diagnostic value in human cancer. Measurements of proton spin-lattice relaxation times (T1) of cellular water protons of normal and malignant esophageal tissues showed elevated T, values in the latter. In some cases, tissues which appeared normal on gross examination assumed as uninvolved tissues had T, values higher than the other grossly uninvolved tissues and often closer to the T, of the corresponding tumor tissue. A histopathological study of the assumed uninvolved areas also studied for the T, values was therefore undertaken. A preliminary study demonstrated the presence of malignant cell groups or clusters in some of the uninvolved samples with higher T1 compared to the true uninvolved tissues, which had a normal histological picture and low T, values. This observation has brought out the importance of histopathological studies in addition to relaxation studies to comprehend contributory factors to relaxation. Secondly, it lends support to the thesis of elevated T, values being characteristics of the malignant state.

13C and 2H spin–lattice relaxation in solid adamantane

1980 ◽  
Vol 58 (7) ◽  
pp. 655-657 ◽  
Author(s):  
Roderick E. Wasylishen ◽  
Brian A. Pettitt
Keyword(s):  
Angular Correlation ◽  
Transition Point ◽  
Relaxation Times ◽  
Proton Nmr ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Nmr Data ◽  
Plastic Phase ◽  
Good Agreement

Spin–lattice relaxation times for the 13C nuclei of adamantane and the 2H nuclei of adamantane-d16 are reported for most of the temperature range of the solid I (plastic) phase, and for the solid II phase just below the transition point. Angular correlation times are shown to be in good agreement with those previously obtained from proton nmr data by Resing.

A study of 14N relaxation and nitrogen–proton spin coupling in Watson–Crick base pair models through Fourier transform measurements on NH proton spin–lattice relaxation in the rotating frame

1979 ◽  
Vol 57 (9) ◽  
pp. 1075-1079 ◽  
Author(s):  
Michael E. Moseley ◽  
Peter Stilbs
Keyword(s):  
Relaxation Times ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Spin Lattice Relaxation ◽  
Indirect Measurements ◽  
Spin Lattice ◽  
Proton Coupling ◽  
Nuclear Spin Lattice Relaxation

Indirect measurements of nitrogen-14 nuclear spin-lattice relaxation times and direct proton coupling constants are presented together with carbon-13 T1 data for a series of alkyl-substituted nucleic acid bases and mixtures thereof in DMSO-d6. With the exception of the guanine NH nitrogen, which possibly experiences a decrease in the electric field gradient upon complexation with cytosine, no indications of significant changes in the electronic environment around the nitrogen nuclei were found for any combination of bases. Forsen–Hoffman spin saturation transfer experiments on the NH and NH2 protons are also presented.

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