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.

The recent application of the shell model theory to the energy level structure of light nuclei has made apparent a lack of experimental data concerning these nuclei. The impossibility of accurately criticizing the theory on the basis of available experimental results has made imperative new investigations to determine the properties of light nuclei. The purpose of this thesis, then, is to present the data obtained in these investigations of light nuclei level structure and to attempt a qualitative explanation of the structure of the mass 9 nuclei by means of a simple model. The data will also be compared to the predictions of the shell theory and, in the case of C12 states, to the predictions of the alpha particle model also.

The purpose of this study is the investigation of the levels in the compound nucleus O17* from an excitation energy of 8.25 Mev to 10.35 Mev by the elastic scattering of alpha particles from C 13. The present work was undertaken in order to complete the assignment of spins and parities. The energy range covered experimentally was from 2.5 Mev to 5.2 Mev alpha particles, which corresponds to excitation energies from 8.25 Mev to 10.35 Mev. For these energies data was taken at four center of mass angles; an analysis of this data was made using the Wigner single-level dispersion-theory form for the scattering matrix. Since the ground state of C13 is 1/2-, and the spin and parity of an alpha particle is O+; the channel spin for this problem is 1/2. For this case the theoretical expression for the differential cross section can be reduced to a compact form for analysis.

Attempts have been made for some time to determine the magnitudes of the individual processes of elastic scattering, inelastic scattering, radiative capture, fission, (n,2n), and other reactions which comprise the total interaction cross section of neutrons. In the energy range of 3 to 15 Mev, which is to be discussed in this paper, the predominant factors of the total cross section are those from elastic and inelastic scattering. This paper is to discuss a method of measuring directly all effects other than elastic scattering, a non-elastic cross section, which is very nearly the cross section for compound nucleus formation.

Because the evidence on the polonium-beryllium gamma ray spectrum is of a somewhat doubtful nature, mainly due to statistical difficulties, it was believed desirable to make a careful investigation of this spectrum with a pair spectrometer. This was made possible by the loan of a two curie polonium-beryllium source from Los Alamos Scientific Laboratory. It was believed desirable also to investigate the gamma spectrum from boron isotopes bombarded with deuterons, since this had never been done with separated isotopes and the assignment of the gamma ray lines to the two isotopes was uncertain. This spectrum gives information on some of the same levels in C12 involved in the Be9(alpha,n)C 12 reaction. The separated B10 isotope was obtained from Oak Ridge National Laboratory.

One of the ways to study the energy levels of nuclei is to measure the energy and relative intensity of the gamma rays produced when different kinds of nuclei disintegrate under charged particle bombardment. This may be of value for several reasons: (1) It may yield information on the manner an excited state decays to the ground state. (2) It may confirm the existence of energy levels for which there is some doubt. (3) Several different reactions may be competing. If the position of the energy levels of the product nuclei are fairly well known, the assignment of gamma rays may be made, and the relative probability for disintegration by various competing channels may be estimated. The gamma rays from most of the light nuclei under proton bombardment have been studied, but the gamma rays from the light nuclei under deuteron bombardment have not been studied so completely. Pair spectrometers, both internal and external, have been used to study the high energy gamma rays from deuteron reactions. The low energy gamma have been studied in the case of Li7 + d, Be9 + d, C12 + d, and C13 + d. In this investigation low energy gamma rays from a number of other light nuclei under deuteron bombardment were studied.

This thesis is divided into two major parts. In the first, "A Cluster Model of the Light Nuclei," a nuclear model is developed which is based on the premise that the light nuclei may be described in terms of two-body clusters of nucleons. A simple mathematical formulation of the model is given and numerical calculations are used to exhibit the properties of this model. In many instances the model's predictions are compared to the experimental data, and possible extensions of the model's usefulness are cited. In the second part, "The Study of Nuclear Properties by Means of Radiative Capture Reactions," the two-body nature of the cluster model is exploited in the calculation of radiative capture transition probabilities. Most of this part is devoted to the analysis of these reactions for the study of nuclear structure; however, some new experimental results are given for the D(p,gamma)He3 and D(alpha,gamma)Li6 reactions.

Abstract Not Available.