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In recent years, there has been a major expansion of high pressure research providing unique information about systems of interest to a wide range of scientific disciplines. Since nuclear magnetic resonance has been applied to a wide spec trum of problems in chemistry, physics and biochemistry, it is not surprising to find that high pressure NMR techniques have also had many applications in these fields of science. Clearly, the high information content of NMR experiments combined with high pressure provides a powerful tool in modern chem istry. It is the aim of this monograph, in the series on NMR Basic Principles and Progress, to illustrate the wide range of prob lems which can be successfully studied by high pressure NMR. Indeed, the various contributions in this volume discuss studies of interest to physics, chemical physics, biochemistry, and chemical reaction kinetics. In many different ways, this monograph demonstrates the power of modern experimental and theoretical techniques to investigate very complex systems. The first contribution, by D. Brinkman, deals with NMR and NQR studies of superionic conductors and high-Tc supercon ductors at high pressure. Pressure effects on phase transitions, detection of new phases, and pressure effects on diffusion and spin-lattice relaxation, represent a few of the topics discussed in this contribution of particular interest to solid state physics.
Molecular reorientation and translation in molecular liquids was studied. A dominant premise in these studies was that, except in strongly hydrogen-bonded systems such as water, the dynamics of a liquid may be considered to be a series of impulsive collisions. Details of the behavior would be dominated by the shape and size of the molecules under constant packing conditions. The second area of effort was in the plastic crystalline solid phase of two globular molecules, adamantane and cyclohexane. The NMR technique was used in these studies to measure self-diffusion coefficients and spin-lattice relaxation times. The applicability of pulsed NMR techniques to the study of the kinetics of order--disorder phase transitions in solid adamantane was demonstrated.
The effect of pressure on exchange rates, of varied systems in condensed media, were observed and typically related to stochastic theoretical models of exchange processes. Rates of exchange were determined using, the total line shape analysis method in chapters two and three, peak areas and saturation transfer in chapter four, and rotating frame spin lattice relaxation measurements in chapter five. Chapter six details some properties of high pressure high resolution NMR probes. Increasing solvent pressure on N,N-dimethyltrichloroacetamide (chapter two) was shown to decrease the rate of rotation about the amide bond. In order to fit the data favorably the Grote-Hynes model, which takes into account the frequency dependence of the friction, was applied. The opposite effect was seen for the rotation of coordinated ethylene in $pi$-cyclopentadienyldiethylenerhodium (chapter three). In this case the data was fit best using the model developed by Skinner and Wolynes. The effect of pressure on the denaturation of lysozyme was determined using the peak areas of the histidine-15$sp{1varepsilon}$ resonance in both the native and denatured forms. The data indicated the possibility of a second major denatured structure under these conditions, while thermal denaturation techniques indicated only one major denatured structure. Individual rate constants of folding and unfolding were also determined using saturation transfer experiments on this same resonance. The effect of pressure on the conformational isomerization of cyclohexane in CS2 was studied using rotating frame spin lattice relaxation techniques (chapter five). By using this method rate constants were obtained which were two orders of magnitude larger than those which could be obtained by the line shaper analysis technique. Increasing solvent pressure increased the isomerization rate by combining this data with previously collected data, it was determined that the barrier to isomerization is pressure independent, and that eyclohexane falls in the inertial regime of the Kramers' model.
The high pressure phase behaviour of binary fluid mixtures has been extensively studied during the last three decades. There is ample experimental data for a wide variety of binary mixtures and extensive methods for prediction have been developed. In contrast, the investigation of ternary and other multicomponent fluids is in its infancy. Experimental ternary mixture critical data are very rare and theoretical studies have been limited to data correlation rather than genuine prediction. The phase behaviour of ternary and other multicomponent fluid mixtures has many novel aspects which are not manifested in binary mixtures. The properties of ternary mixtures are also likely to be more difficult to characterize experimentally. It is in this context that calculated phase diagrams have an important role in leading the discovery of new phenomena and guiding experimental work. The criteria for phase equilibria of multicomponent fluids with particular emphasis on the critical state are examined in this book, and models for predicting fluid equilibria (e.g., different equations of state) are compared. Particular attention is paid to the critical state of ternary mixtures which has hitherto been largely neglected. The problems associated with predicting ternary equilibria are discussed, and some novel aspects of ternary critical phenomena are illustrated. The books also describes a novel type of critical transition which appears to be a common feature of the equilibria of ternary mixtures. Extensive phase diagrams of a wide range of ternary mixtures including systems containing carbon dioxide, water, nitrogen and tetrafluoromethane as one or more component are presented. The theoretical treatment is detailed in the appendix and a computation of known experimental critical points is also included.
Pressure, like temperature, is one of the most important parameters governing the state of matter. Today, high-pressure science and technology is applied to diverse research fields: physics, chemistry, biology, earth and marine sciences, material science and technology, chemical engineering, biotechnology and medicine. Research on liquids and solutions at high pressure is not only important for elucidating the structure of liquids, intermolecular interactions between solutes and solvents and chemical reactions in solutions, but also for providing fundamental numerical data for the design of chemical plants and the development of chemical processes. In particular, high-pressure studies of water and aqueous solutions are closely correlated with research into bioscience and biotechnology. In this volume some of the most important and most recent advances in liquids and solutions at high pressure in Japan are presented.