Abstract Not Available.

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.

Abstract Not Available.

Abstract Not Available.

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.

Abstract Not Available.

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.

The method to be discussed here is that of measuring the threshold energy for neutron production. Extensive discussions of this method are to be found in the literature. In particular we are concerned with neutrons resulting from deuteron bombardment.

The NMR spectrum of solid hydrogen (75% ortho) has been studied as a function of temperature from 1.2°K to 14°K and of pressures from one to three hundred atmospheres. At about 10°K the absorption signal broadens from less than one gauss to 5.3 gauss between slope extrema as the temperature is lowered and self diffusion ceases. When pressure is applied, this broadening is shifted to higher temperatures by a sizeable amount. With 230 atmospheres, a shift of 3.2°K was observed. Correlation times and activation energies of self diffusion have been computed for each of the transitions at various pressures. The activation energies are linearly dependent upon the transition temperatures. The lower transition at 1.5°K in which some rotational degeneracy is removed was also investigated with various pressures. Pressures up to 216 atmospheres did not shift the transition temperature to any observable extent. Pressures up to 337 atmospheres had no effect on line shape below 1.5°K.

The nature of the interaction between a neutron and an atomic nucleus depends upon the characteristics of the nucleus involved. Consequently some information concerning nuclear structure can be derived from studies of the scattering of neutrons by nuclei. The experimental observations can be compared with the theoretical predictions and may support the theory or suggest a different approach to the theoretical problem. One method of studying neutron scattering is to observe in a cloud chamber the tracks produced by nuclei recoiling from collisions with the neutrons. From measurements of the lengths of the recoil tracks and their angles with respect to the incident neutron direction, the distribution of the scattered neutrons in angle and energy may be deduced.