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Magnetic susceptibility measurements have been made on a series of nickelous oxide samples prepared by the decomposition of hydrous nickel hydroxide at temperature levels of 250°--1300°C, the crystal size varying from 80--2000 A. The magnetic studies show a lowering of the antiferromagnetic transition temperatures and an enhanced non-Curie-Weiss effect as the temperature of heat-treatment and the particle size is decreased. It has been found that these effects are related to the increase in the ratio of the specific surface to the specific volume as the crystal size decreases, thereby decreasing the average number of next nearest magnetic neighbors, producing a change in the magnetic environment of the surface atoms, hence drastically altering the magnetic properties.

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The technique of adiabatic fast passage has been employed to measure within +/-1% the susceptibility of pure He3 and some He3--He4 mixtures for temperatures between 0.9°K and 3.0°K. Above 1.2°K the susceptibility varies as the inverse of the temperature, indicating that the statistical and exchange correction to the Curie susceptibility is very nearly constant. We have calculated the magnetization of an interacting system of He 3 particles near the classical limit. Plane waves have been used to evaluate the potential energy and the exchange energy of the particles. In this approximation potential correlation is handled by the introduction of a cutoff radius a. For reasonable choices of the cutoff, the statistical correction and the exchange correction are of comparable magnitude.

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The measurement of gamma-rays emitted by nuclei under heavy particle bombardment is an important source of information concerning nuclear level structure. Unfortunately, in the region of light nuclei the gamma-ray energies are large and their accurate measurement is difficult. Most high energy gamma-ray measurements in the past have been made with detectors of such poor resolution as to obscure the details of complex spectra. For this reason considerable effort has been expended to improve the performance of a magnetic lens pair spectrometer for gamma-ray measurements. Sufficient progress has been made so that it was thought worth while to survey the gamma-rays from a number of nuclear reactions with the instrument in its present form. The results reported here together with those of R. D. Bent (Ph.D. Thesis) constitute such a survey. In addition to the measurement of gamma-rays the spectrometer provides a means of detecting nuclear pairs ejected in J = 0 to J = 0 transitions. A specific attempt was made to detect such pi states in the several nuclei where they have been proposed.