The deuteron quadrupolar relaxation is studied for some liquids. As the spin—lattice quadrupole relaxation depends on the electric‐field gradients (efg) at the nucleus the experimental values of T1 have been used in order to obtain the field gradients at the hydrogen site in the benzene and acetone molecules. For this purpose, the correlation times for the molecular motions responsible for the quadrupolar relaxation have been estimated from proton magnetic relaxation measurements in mixtures of the liquid with its perdeuterated analog. A theoretical evaluation of the efg tensor has also been performed by using MO's in the LCAO approximation with Slater's orthogonalized AO's. The agreement between the theoretical evaluation and the experimental results is more than satisfactory and it seems to confirm a certain validity of the wavefunctions and the method of calculation used. For chloroform a calculated efg tensor has been used to obtain a value for the reorientational correlation time from the deuteron sp...

Electric‐Field Gradients in Liquids by Deuteron Quadrupole Relaxation

The apparatus for the adiabatic fast passage experiments used for the measurement of NMR spin‐lattice relaxation times is described. The different experimental conditions and techniques for the T1 measurements of chemically shifted nuclei are briefly discussed.

Adiabatic Fast Passage Method for Spin‐Lattice Relaxation Time Measurements

T1 and T2 proton relaxation times were measured for the chloroethanes (CH3CH2Cl, CH3CHCl2, CH2ClCH2Cl, CH3CCl3, CH2ClCHCl2, CH2ClCCl3, CHCl2CHCl2, and CHCl2CCl3) at room temperature as a function of concentration in CS2. The data was extrapolated to infinite dilution. The extrapolated relaxation times were interpreted in terms of two mechanisms: internal dipolar interactions, and scalar coupling between proton and chlorine nuclei. The extrapolated relaxation times indicated that the dipolar correlation times increased as the number of chlorines increased, while the chlorine relaxation times decreased as the number of chlorines increased. Internal dipolar correlation times were computed from the extrapolated T1 relaxation times. The relative trends of the reorientational correlation times were explained equally well by the BPP viscosity model and an inertial model due to Steele. The inertial model predicted correlation times which were too low by a factor of 2, whereas the BPP model predicted correlation t...

Proton Spin Relaxation in the Chloroethanes

12 – measurement of relaxation times

This is a description of a method for measuring long spin-lattice relaxation times. It is based on a series of adiabatic fast passages and is particularly convenient in the case of exceptionally long times.

A method for the measurement of long spin-lattice relaxation times

A method for measuring transverse relaxation times in liquids is described. The method is based on the observation of the decay of the nuclear magnetization when it precesses in a plane perpendicular to the constant magnetic field. This condition is realized by stopping the variation of the constant magnetic field during a fast adiabatic passage at a proper time. The constant magnetic field is modulated with a sawtooth current from a relaxation oscillator and an amplifier. When the voltage induced by the nuclear precession reaches a fixed value the relaxation oscillator is stopped with a delay such that the constant field stops its variation at the value for which the signal has the largest amplitude. Measurements have been made on some pure liquids and the preliminary results indicate that the values ofT
2 are very close to those ofT
1.

A method for the measurement of the nuclear transversal relaxation time

A method for measuring transverse relaxation times in liquids is described. The method is based on the observation of the decay of the nuclear magnetization when it precesses in a plane perpendicular to the constant magnetic field. This condition is realized by stopping the variation of the constant magnetic field during a fast adiabatic passage at a proper time. The constant magnetic field is modulated with a saw-tooth current from a relaxation oscillator and an amplifier. When the voltage induced by the nuclear precession reaches a fixed value the relaxation oscillator is stopped with a delay such that the constant field stops its variation at the value for which the signal has the largest amplitude. Measurements were made on some liquids and the preliminary results indicate that the values of T/sub 2/ are very close to those of T/sub 1/. (auth)

L. Giulotto

Papers

A method for the measurement of the nuclear transversal relaxation time

A METHOD FOR THE MEASUREMENT OF THE NUCLEAR TRANSVERSAL RELAXATION TIME. Final Technical Report No. 1 for February 1958-January 1959