Chiral Interferometry and Density Functional Theory of Magnetic Responses

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Professor Robert Harris of the University of California, Berkeley is being supported by a grant from the Theoretical and Computational Chemistry Program to continue his research in two distinct areas. The first deals with the existence of superpositions of handed molecules, while the second deals with magnetic responses in molecules. A basic consequence of quantum mechanics is the existence of superpositions of handed molecules. Until recently there were no suggestions as to how to prepare these fundamentally quantum objects. Harris has very recently advanced an elementary theory of how the superpositions may be prepared, and their coherence assessed. One purpose of the proposed research is to generalize both the idea of these coherences and construct more realistic and varied ways of preparing and measuring them. Given their production in a variety of conditions, it is proposed to investigate the behavior of these superpositions. In particular, the PI will examine how they collide with other systems, as well as how their coherence degrades in condensed matter. Finally, rotational coherences which are chiral will also be investigated. The second area involves magnetic responses in molecular systems which historically involves calculating diamagnetic and paramagnetic contributions separately. A recently proposed magnetic field density functional theory emphasizes that density functional theory allows, in principle, a gauge invariant theory to be automatically constructed. In addition, all responses are universal functionals of the electron density in the absence of magnetic fields. Calculations of magnetic responses will be carried out. In addition, a theory of changes in electron density due to distant groups and their relation to magnetic responses, will be constructed. The first aspect of this work deals with the existence of superpositions of handed molecules, which arrises as a basic consequence of quantum mechanics. Until recently there were no suggestions as to how to prepare these fundamentally quantum objects. The PI and his colleague J.Cina, have very recently advanced an elementary theory of how the superpositions may be prepared, and their coherence assessed. In work to be carried out, a detailed theory will be constructed for real molecules so that experiments may be carried out. A second purpose is to see how the excited state photochemistry, which is a consequence of the superpositions, differs from that of ordinary handed molecules and mixtures of those molecules. The second aspect of this work deals with Nuclear Magnetic Resonance. (NMR) is used to determine the structure of a variety of molecules and more complex systems such as proteins and RNA. The assessment of these structures is based on the variation of the NMR parameters of the system with changes in geometry and environment. The research proposed is based on a new method by the PI for calculating in a systematic way the NMR parameters. The method is based on the electron density of the system, and how it changes with geometry and environs. This way of looking at NMR parameters has no precedent and should be useful in the construction of the electron density itself.