Distorted-wave Born-approximation (DWBA) analysis of direct reactions has proven to be a very useful tool in understanding single- and two-particle transfer reactions and nuclear structure. The 4 MV Van de Graaff accelerator at Virginia Polytechnic Institute and State University was used to check the feasibility of DWBA analysis on the (d, α) reaction at low bombarding energies for medium weight nuclei where compound nuclear contributions are expected to be present. An excitation function is measured on the ⁴⁴Ca(d, α)⁴²K reaction with incident bombarding energy ranging from 3.3 to 4.0 MeV. The angular distributions obtained from this reaction at 4.0 MeV bombarding energy and with a range of angles from 40° to 160°, are presented for the five strongest levels of ⁴²K along with the DWBA fits. The satisfactory DWBA fits and the L transfers predicted thereby, indicate that this type of analysis might indeed be useful. One good indication is by no means conclusive and more work of this type is needed to substantiate the results found here. / Ph. D.

This thesis contains an account of a measurement of the neutron energy spectrum from radiative pion capture in carbon, oxygen and calcium. The measurement was performed at six n-γ correlation angles for the case of carbon and oxygen, and seven n-γ correlation angles for the case of calcium. The observed energy spectra fall off approximately exponentially between 2 and 30 MeV. Evidence of resonance structure was observed at about 4 MeV in the energy spectra of carbon and oxygen. This is in agreement with a theoretical prediction of the giant multipole excitation model. The neutron yield versus n-γ correlation angles peaks at 180° for all three nuclei studied. This indicates the quasi-free mechanism also plays an important role in the radiative pion capture process. / Ph. D.

Standard methods of scintillation spectroscopy were used to investigate the decay scheme of Kr⁸⁷. Natural krypton gas, containing 17 percent Kr⁸⁶, was irradiated in the 100 kilowatt V.P.I. research reactor to produce Kr⁸⁷ Which decays by beta emission to Rb⁸⁷. The halflife of Kr⁸⁷ was found to be 78 minutes in agreement with other investigators. Gamma spectra and gamma-gamma coincidence measurements employed two integral line NaI(Tl) detectors with 3 in. diameter by 3 in. long crystals. Beta measurements were made using a 2 in. diameter by 1/2 in. long CaF₂(Eu) integral line detector. Both the gamma spectrum and the beta spectrum were found to be complex. Energy values of 0.40, 0.85, 1.57, 1.75, 2.42, 2.97, and 3.30 MeV were assigned to excited states in Rb⁸⁷. Possible parities and spins were assigned to most of the excited states from beta-ray log ft values. End-point energies of the beta groups populating the ground state and the first and second excited states were measured and used in conjunction with the gamma-ray energy measurements to calculate a value of 3.85 ±.04 MeV for the Kr⁸⁷ disintegration energy. Gamma-ray relative intensity measurements provided a percent abundance estimate of the beta groups populating the various Rb⁸⁷ energy levels. Angular correlation measurements were performed for the 2.57 - 0.40 MeV gamma-gamma cascade proceeding from a level at 2.97 MeV. The results were consistent with log rt and shell model predictions and allowed a tentative assignment of 9/2⁺ to be made for this state. The ground state spin and parity or Kr⁸⁷ is inferred, on this basis, to be 7/2⁺. / Ph. D.

Using a stack of multiwire proportional chambers with interspersed absorbers, the ranges and directions of low energy pions and muons have been measured. By simultaneously determining both the directions of negative muons incident upon and scattered from thin sheets of galvanized steel, aluminum, and polyethylene, and the ranges of these muons in the proportional chamber stack, their multiple scattering as a function of energy has been obtained. The measured rms projected multiple scattering angle was fitted to a linear function of the values predicted by the Moliere theory: θ^proj_rms (expt.) = C[θ^proj_rms(theor.)] ± D. The results were C = 0.861 ± 0.012, D = 0.219° ± 0.176° for galvanized steel (thickness 0.608 gm/cm²); C = 1.05 ± 0.05, D = -0.148° ± 0.126° for aluminum (0.429 gm/cm²); and C = 1.02 ± 0.06, D = 0.259° ± 0.086° for polyethylene (0.297 gm/cm²). Also the range distributions of positive muons and positive and negative pions at various energies were measured, and the mean range and range straggling (deviation about the mean) were obtained and compared with the calculations of Janni •. The percent differences between the actual incident energies (measured in a magnetic spectrometer) and those calculated from the mean range were 2.37% for 39.32 MeV µ⁺, 1.31% for 37.62 MeV π⁺, 0.608% for 33.00 MeV π⁺, 0.303% for 33.00 MeV π⁻, and 0.854% for 37.62 MeV π⁻. These results are all within the expected accuracy of the range calculations~ The ratios of the observed to the predicted range straggling for the corresponding particles and energies were 1.00, 1.20, 1.40, 1.40, and 1.20. The straggling of pions may appear to be 20-40% larger than range theory predicts perhaps because of the. effects of the strong interactions of pions with the nuclei of atoms in the stopping material. / Ph. D.

A transmission electron microscopy study involving direct and replicating techniques is directed to a definition of the microstructure of radio frequency-sputtered, thin lead-dielectric cermet films. Once defined, this microstructure is used to obtain theoretical film refractive indices. The Maxwell Garnet theory provides a basis for the theoretical results. Measurements of film transmission and reflectivity are used to obtain rough experimental values for film refractive indices by the Tekucheva method. More exact values are obtained via ellipsometry. The rough Tekucheva values are used to determine the range over which computer calculations interpreting the ellipsometric results must be made. This technique yields accurate values for the film refractive indices. The films are radio-frequency-sputtered from lead glass targets with varying amounts of lead attached to their faces. Three different targets are used, resulting in three sets of films, each containing a different percentage of lead. The lead content of the films is measured by microprobe analysis as well as visual inspection of micrographs. The lower content lead films are seen to consist of tiny balls of lead embedded in the dielectric, as are the intermediate lead content films; but the higher lead content films form metallic networks throughout the dielectric. The lower and intermediate lead content films have indices which agree with the predictions of the Maxwell Garnett theory; but the higher lead content films, whose structure fails to conform to the Maxwell Garnett configuration, have indices whose values diverge from the Maxwell Garnett predictions. It is thus shown that the theory of Maxwell Garnett is valid for thin cermet films whose structure consists of tiny metal balls embedded in a dielectric medium. / Ph. D.

A variational energy calculation for an N-particle boson system has been performed. A two-body Hamiltonian, containing the phenomenological Lennard-Jones 6-10 potential, has been assumed, and the parameters of the Lennard-Jones potential have been chosen appropriate for liquid helium II. The trial wave function was assumed to be of the Jastrow type with two parameters. The value of one of the parameters was chosen to satisfy a liquid-structure-factor consistency condition. The expectation value for the ground state energy is expressed in terms of a generalized normalization integral. To evaluate the 3-N fold integrals, the normalization integral is approximated by truncating its expansion. After performing the variation, the ground-state energy is expressed as a function of the reduced particle number density. The cluster approximations used were found insufficient to effect saturation. / M.S.

M.S.

M. S.

The state of polarization of neutrons emitted at an angle of 45° (Lab) from the D(d,n)He³ reaction has been determined by observing the asymmetry in scattering from carbon. Neutrons scattered at equal angles to the right and left were detected simultaneously by two cylindrical stilbene crystals, The neutrons were produced by bombarding a heavy ice target with an unanalyzed beam of deuterons from a Cockroft-Walton accelerator. The phase shifts of Meier, Scherrer, and Trumpy* were used to compute the induced polarization of carbon at an average neutron energy of 2.7 Mev. The observed asymmetries in scattering yielded neutron polarizations of 11.1 * 1.5%, 7.8 * 1.4%, and 6.0 * 1.8% at average deuteron energies of 99 Kev, 81.5 Kev, and 67.5 Kev respectively. Polarized neutrons (2.73 Mev) scattered from calcium indicated that the right-left asymmetry, P_nP_Ca changes sign in the interval 87.5° to 120° (CM). P_Ca ≤ 61.7% in the interval 0° to 180° (CM). * Meier, R. W., Scherrer, P., and Trumpy, G., "Elastische Streuung und Polarisationseffekte von D-D Neutronen an Kohlenstoff", Helv. Phys. Acta 27, 577 (1954). / Ph. D.

Using a new and unique multiparticle detection device, we have measured the average final state multiplicity for a sample of 1,500 events from the reaction pp → pp (nw<super>±</super>) at 28.5 GeV/c where both protons were constrained to limited regions of phase space. We find that the resulting average charge multiplicity depends linearly on the recoil mass from both protons, and on the inelasticity. A rapidity analysis indicates that low multiplicity final states are produced by one fragmenting proton, while as the multiplicity increases, so does the probability of the other proton also fragmenting. No evidence was found for multiperipheral production. We compare our data with events in which only one proton is constrained and find that the multiplicity varies with the behavior of both final state protons, the higher multiplicities occurring for more central collisions. / Ph. D.