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The spin—lattice relaxation time T1 of 19F was measured over a temperature range of 77° to 1300°K in natural and synthetic CaF2 crystals and in CaF2 crystals doped with 0.05% Sm, 0.16% Sm, and 1.20% Sm. Most of the data was taken with the magnetic field along the [100] and [111] directions using the magnetic recovery method. For annealed samples T1 at room temperature and below is found to be inversely proportional to the concentration of samarium. Measurements show that in the high-temperature regions T1 is primarily governed by translational diffusion. Activation energies in the extrinsic and intrinsic regions were found to be 0.36 and 2.3 eV, respectively, for the pure sample and 0.53 and 2.4 eV for the doped samples. These are in good agreement with the activation energies obtained from conductivity measurements. The knee separating the extrinsic and intrinsic regions occurred at higher temperatures as the amount of dopant was increased. The T1-vs−1/T curves had a minimum at 1120°K for all the samples. Below 400°K T1 was found to be directly proportional to temperature for the doped samples. The low-temperature data indicate that the correlation time of samarium at room temperature is of the order of 10−14 sec.

A series of sulfur compounds have been examined by 33S NMR at 15.3 MHz. The sharpest resonances were found for the inorganic sulfates, with line widths varying from 3.6 Hz for ammonium sulfate to 9.0 Hz for sodium sulfate. Increasing the viscosity of the solvent did not affect the line widths appreciably. Other anions and molecules examined, and their corresponding line widths, included cysteic acid (30 Hz), sodium thiosulfate (60 Hz), ammonium sulfamate (300 Hz), carbon disulfide (400 Hz), concentrated sulfuric acid (1200 Hz) and dimethyl sulfate (2000 Hz). A comparison of the measured line widths and the spin‐lattice relaxation times, T1, for five of these samples indicated that exchange processes may contribute to and often dominate the 33S resonance line widths in aqueous samples. No signals were observed in concentrated aqueous solutions of cysteine, adenosine monosulfate or chondroitin sulfate after overnight scans.

The hydrogen nuclear magnetic relaxation time (T1) for degassed samples of several organic liquids has been measured, by a transient method, at pressures up to 1400 kg/cm2, primarily for comparison with results obtained without degassing. Certain of the liquids were investigated, without degassing, by Benedek and Purcell, who concluded that T1 decreases under pressure less rapidly than the rates of translational processes (fluidity and diffusion). The present results confirm this for degassed methyl iodide and n-heptane, in both of which the effect of degassing is to increase T1 less than 20%. For benzene and toluene, degassing causes T1 to increase by several hundred percent, and the preceding conclusion ceases to apply, but instead, in the degassed samples, the relative rate of decrease of T1 under pressure is comparable to that of the fluidity; in benzene, at low pressures, it is greater. Additional pressure studies are reported for purified cyclohexane, for purified 1,1,1-trichloroethane, and for chloroform, which was not successfully purified.

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