Thesis. The variational equation is derived and discussed using Jastrowtype wave functions, which are a product of pair wave functions, as the trail wave function. The various approximations used in simplifying the variational equations so as to obtain a form that is possible to solve numerically are discussed also. A Monte Carlo calculation is described using the wave function obtained. Exchange in /sup 3/He is discussed. (MHR)

In Chapter I we present the results on a study of cross polarization dynamics, between protons and carbon-13 in adamantane, by the direct observation of the dilute, carbon-13, spins. These dynamics are an important consideration in the efficiency of proton enhancement double-resonance techniques and they also provide good experimental models for statistical theories of cross relaxation. In order to test these theories we present a comparison of the experimental and theoretical proton dipolar fluctuation correlation time {tau}{sub c}, which is experimentally 110 {+-} 15 {micro}sec and theoretically 122 {micro}sec for adamantane. These double resonance considerations provide the background for extensions to deuterium and double quantum effects discussed in Chapter II. In Chapter II an approach to high resolution nmr of deuterium in solids is described. The m = 1 {yields} -1 transition is excited by a double quantum process and the decay of coherence Q({tau}) is monitored. Fourier transformation yields a deuterium spectrum devoid of quadrupole splittings and broadening. If the deuterium nuclei are dilute and the protons are spin decoupled, the double-quantum spectrum is a high resolution one and yields information on the deuterium chemical shifts {Delta}{omega}. The relationship Q({tau}) {approx} cos 2{Delta}{omega}{tau} is checked and the technique is …

Mathematical descriptions of an excited state multilevel system are developed to include progressively the effects of coherent coupling, feeding, decay and relaxation, and the expressions are illustrated with several pulse coherence experiments utilizing zero field optically detected magnetic resonance of excited triplet states. A new method is described in which the time development of the coherent components in a multilevel system is monitored by using an observable that can measure only relative populations between the levels. The method is illustrated. By treating a coherently driven excited state system as two levels in contact with a population reservoir, exact expressions are obtained for both transient and steady-state behavior in the presence of transverse and spin lattice relaxation, constant incoherent pumping, spontaneous emission between the two levels, and also decay back into the reservoir. The general mathematical development is applied specifically to zero field microwave phosphorescence double resonance. Experimental methods and apparatus are discussed in detail and results of optically detected transient mutations, spin echoes, and Fourier transform spectroscopy are presented. (26 figs, 220 refs) (auth)

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The effect of alkaline solutions containing dissolved oxygen on coal-derived pyrite was investigated in a tubular reactor. The rate of total sulfur conversion seems to be affected by oxygen partial pressure, oxygen flow rate, particle size, pyrite charge size and system temperature. A shrinking core model was chosen to represent this chemical leaching process. From the results obtained, it seems that ash or product-layer difusion is the rate-limiting step for leaching with the alkaline solution/oxygen system. The effective diffusivity is about 10/sup -5/ cm/sup 2//sec. The apparent activation energy for this process is 7.97 kcal/mole in the temperature range from 121/sup 0/ to 175/sup 0/C. For the tubular reactor system used, the rate of sulfur extraction appears to be proportional to the oxygen partial pressure. The rate of conversion increases as the oxygen flow rate decreases to a limit of 3 ml/sec. The rate also increases as the pyrite charge size decreases. The leaching solutions flow rate has a negligible effect on the total sulfur conversion.

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The effect of free-particle collisions in simple ''knockout'' reactions of the form (a,aN) and in more complex nuclear reactions of the form (a,X) was investigated by using protons and pions. Cross sections for the $sup 48$Ti(p,2p)$sup 47$Sc and the $sup 74$Ge(p,2p)$sup 73$Ga reactions were measured from 0.3 to 4.6 GeV incident energy. The results indicate a rise in (p,2p) cross section for each reaction of about (25 +- 3) percent between the energies 0.3 and 1.0 GeV, and are correlated to a large increase in the total free-particle pp scattering cross sections over the same energy region. Results are compared to previous (p,2p) excitation functions in the GeV energy region and to (p,2p) cross section calculations based on a Monte Carlo intranuclear cascade-evaporation model. Cross section measurements for ($pi$/sup +-/, $pi$N) and other more complex pion-induced spallation reactions were measured for the light target nuclei $sup 14$N, $sup 16$O, and $sup 19$F from 45 to 550 MeV incident pion energy. These measurements indicate a broad peak in the excitation functions for both ($pi$,$pi$N) and ($pi$,X) reactions near 180 MeV incident energy. This corresponds to the large resonances observed in the free-particle $pi$$sup +$p and $pi$$sup -$p cross sections at the …

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The use of high rate anodic dissolution (electrochemical machining) for shaping titanium carbide, zirconium carbide, titanium boride and zirconium boride has been investigated in 2N potassium nitrate and 3N sodium chloride under current densities ranging from 20 to 120 A/cm{sup 2} (corresponding to cutting rates of 0.3 to 1.8 mm/min). The dissolution stoichiometry for all these materials is independent of the current density in the range 20 to 120 A/cm{sup 2}. Both titanium and zirconium appear to dissolve in the +4 state, boron in the +3 state and the weight loss measurements indicate that carbon is oxidized to CO and CO{sub 2}. The current voltage curves permit to establish that, over the entire current density and flow range investigated, dissolution occurs in the transpassive state. The surface roughness obtained on TiC and ZrC is within 3-5 {micro}m and is independent of current density, applied voltage or flow rate.

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An experimental investigation was carried out to improve the froth flotation method of separating coal pyrite. The effect of several surface active agents on the floatability of an Iowa coal and its associated pyrite was studied in both the presence and absence of methyl isobutyl carbinol (MIBC), a commonly used frother. The effectiveness of a special method of chemical pretreatment for depressing pyrite was also investigated. The zeta potential of the same coal and pyrite was measured under the same conditions used in the flotation tests (in the absence of frother). In the absence of MIBC, the floatability of coal and pyrite was low, and appeared to depend on pH. The maximum recovery of pyrite was obtained at a pH of 4.5 with recovery being less at higher or lower pH. The addition of a small amount of MIBC significantly increased the recovery of coal and pyrite with the increase in the recovery of coal being much greater than the increase in the recovery of pyrite. Also in the presence of MIBC, the floatability of coal and pyrite seemed to be affected more by pH than in the absence of MIBC. On the other hand, several potential pyrite depressants were …

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Thesis. The effect of spall impact, site configuration, and the material properties of rocks at the blast site on the generation of Rayleigh waves by underground nuclear explosions was examined by experimental and computational methods. The hypothesis was that the impact of earth and rock, i.e., spall, falling back after being kicked up by the initial shock wave of an explosion is a source of surface waves observed from explosions. A comparison of amplitudes derived from spall momentum with observed Rayleigh amplitudes at ranges of from 50 to 500 km showed that the spall has sufficient impulse to account for these waves. In the site configuration studies it was found that the strongest signal was produced by a horizontally distributed source placed beneath a mountain, and the weakest signal was produced by a concentrated source placed beneath a flat plain. The horizontal dimension of the source had the biggest effect on the Rayleigh amplitude. Based on laboratory measurements of the mechanical properties of rocks in drill cores from the Boxcar and Gasbuggy sites, calculations were made of the spall impulse and surface displacement profiles from these explosions. The numerically obtained profiles were in reasonable agreement with values inferred from accelerometer …

Thesis. Two polarizable ion models are developed to describe the gas phase of metal dihalide molecules. Both models use electrostatic and repulsive interactions to predict molecular geometries and molecular constants. The first model is applied to the dihalides of the alkaline earths, group II-b metals, transition metals, group IV-a metals, and europium. In addition to the molecular geometry, bending frequencies are derived for most of these molecules. The second or linear'' model is applied to the alkaline eanth dihalides; equilibrium internuclear bond lengths, stretching force constants, and stretching frequencies are determined. (LK)

The groundwater effects of surface mining at ICP No. 1 can be classified primarily as water quality and water quantity effects. The water quantity effects are: the loss of groundwater saturation in spoil materials that were initially removed from over the coal and later replaced; the dewatering of high permeability geologic strata up gradient of mining area; the increase in porosity and possibly permeability in refilled spoil materials; and the change in groundwater gradients in mined areas and near the sediment pond. The water quality effects are: the generation of slightly mineralized enclaves near the sediment pond and spoil accumulations; the generation of thin zones of highly mineralized water near the base of reclaimed spoil probably due mostly to remnant acid mine water; and reduction of water quality in coal seams as a result of dewatering at the time of mining and subsequent oxidation of their pyrite content. Most effects of water quantity loss in and around the mine are not permanent. Water quality disturbances of the fringe areas of reclaimed mine areas will be very slow in attenuating because of the slow groundwater flow through these materials. Adulterated groundwaters in high permeability areas such as the flood plain alluvium …

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The kinetics of the methanation reaction were measured on thin ruthenium films in the temperature range 548 to 623K. The pressures of the reactant gases were varied over the ranges 1.5 to 1500 ..mu..m for CO and 300 to 75000 ..mu..m for H/sub 2/ to yield kinetic orders for each gas. The CO kinetic order varied from +1 at low pressures to -2 at high pressures. As the H/sub 2/ pressure was increased its kinetic order varied from +2 to -1. Both of these order plots had unusually sharp maxima. The reaction is zero order in both CH/sub 4/ and H/sub 2/O. The apparent activation energy was dependent upon temperature with a value of 21.9 kcal/mole at 573K. Auger spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) indicated that the surface was always covered with carbon. This carbon could be divided into two types based upon its reactivity toward hydrogen. Type-1 was very reactive to 3.5 torr hydrogen doses at 573K and was completely removed in less than 300 seconds. Type-2 was less reactive and required about 48 hours under the same conditions for removal. No oxygen was ever detected on the surface after methanation. Low energy electron diffraction (LEED) and …

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Three investigations of difference frequency generation (DFG) of far-infrared radiation by optical mixing are described: a theory of DFG by monochromatic, focused Gaussian pump laser beams, a theory of DFG by a picosecond pump laser pulse, and an experiment using ruby-pumped dye lasers. First, the theory of far-infrared generation by optical mixing of monochromatic, focused Gaussian beams in a uniaxial crystal is developed, taking into account the effects of diffraction, absorption, double refraction, and multiple reflections and total reflection at the boundary surfaces. (Reflection and transmission coefficients of a uniaxial crystal slab are derived by a new matrix technique.) Results of numerical calculations are presented. Focusing the pump beams appreciably enhances the far-infrared output despite the strong far-infrared diffraction. In a 1-cm long crystal, the optimum focal spot size is approximately equal to or smaller than the far-infrared wavelength for output frequencies less than 100 cm{sup -1}. Double refraction of the pump beams is relatively unimportant. Both far-infrared absorption and boundary reflections have major effects on the far-infrared output and its angular distribution. The former is often the factor which limits the output power. We show that a simple model treating the nonlinear polarization as a constant lie-radius Gaussian distribution …

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