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.

Abstract Not Available.

Varied techniques have been employed for the production of nuclei in excited states. The techniques that are suitable vary with the nucleus to be studied and the nature of the particles which are emitted. Ordinarily, the desired excitation can be produced by bombarding the nucleus with light weight nuclear particles. If the incident particle is charged then it is necessary to have a more energetic particle than if the incident particle was uncharged, since it must penetrate the repulsive effects of the Coulomb field of the target nucleus. This effect can be eliminated by using neutrons to excite the nuclei, but if charged particles are used for the nuclear excitation then it is necessary to have some device to accelerate them to high kinetic energies. In the region of light weight target nuclei, a number of accelerators will suffice. The Van de Graaff and the Cockroft-Walton electrostatic accelerators have been satisfactorily used, whereas for heavier target nuclei various types of cyclotrons and linear accelerators have proved useful. In the past few years the development of Van de Graaff accelerators capable of achieving higher energies has led to the experimentation on medium Z nuclei. The Rice Institute 5.5 Mev Van de Graaff generator is suitable for such work and has been used in the experiments to be discussed here to study the excited states in some of the isotopes of iron, nickel, manganese, and copper.

The general theory for beta decay is developed in section 2 using a consistent normalization and phase convention for the lepton wave functions; these phases are not consistent in the literature. The resulting general expression is specialized in section 3 to the case of beta polarization; that is, the nucleus is assumed randomly oriented before and after the transition, and no information is available on the direction of motion of the neutrino. In section 4, the functions needed to calculate the polarization are expanded in powers of the nuclear radius, without using the low-Z approximation. Formulas for these combinations of the electron wave functions are given (for the spectrum) more generally than they have previously appeared; those needed for the polarization have not been given accurately before. In terms of these combinations, expressions for the spectrum and polarization terms of the transition probability are presented, through second forbidden transitions. Somewhat simplified expressions, but retaining more accuracy than the usual low-Z formulas, are also given for the allowed and first forbidden transitions. The results of a numerical evaluation of the spectrum and polarization are compared in section 5 with the low-Z approximate values. These approximate values for the polarization are found to be extremely good, even when the results for the spectrum differ by a factor of two! The expression for the polarization is a ratio of similar terms, and the higher coulomb corrections cancel nearly completely. The effect of the coulomb field on the forbiddenness expansion is considered in section 6, and the application of polarization measurements to tests of time reversal is discussed.