[en] The first half of this dissertation studies reactive intermediates which were formed in rare-gas matrices using epr matrix isolation spectroscopy. In particular, the reactions of lithium with small molecules were studied at liquid helium temperatures in argon matrices. A theoretical study of the bonding involved in the Li-H₂O species was studied, as an example of the lithium-Lewis Base reactions, using restricted Hartree-Fock theory. In addition, the theory is used to calculate the change in spin density, relative to the free atom, which occurs when lithium forms a complex with water. Three different basis sets were used in order to determine the sensitivity of the spin density to the basis set selection. The second half of this disseratation involves theoretical studies of the interactions between a proton and rare-gases. The total interaction energy between a proton and one or two helium atoms is resolved into electrostatic, polarization, and charge-transfer energy components. A general model is described for determining the long-range interaction energies in proton rare-gas clusters by separately calculating the individual components

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[en] The author considers the spin-density enhancement in the framework of a model which allows an analytical investigation of the spin-polarization induced by an external field. (Auth.)

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[en] The constant muon polarization for anomalous muonium exhibits a peculiar field dependence which represents an easily measurable signature of anomalous muonium centers even in polycrystalline materials. Furthermore it can be used to extract information on the dynamical destruction of the state upon temperature variations and it might also be useful to investigate muonium in amorphous materials

[en] The local electronic structure of La₂CuO₄ has been determined using first-principles cluster procedures. Spin polarized calculations with the density functional method with generalized gradient corrections to the correlation functionals have been performed for various clusters containing up to nine copper atoms. The resulting electric field gradients and magnetic hyperfine coupling parameters are in good agreement with experiment. We then have extended the clusters by inclusion of a hydrogen (muon) at various selected sites and have determined the total energy allowing for lattice relaxation of neighboring atoms. The hyperfine fields at the muon transferred from the copper ions have been evaluated. The results are compared with those at previously suggested muon sites

[en] The enhancement of conduction electron density at the position of a positive muon implanted into a metal is calculated in a simple model. Some problems in the interpretation of muon spin frequencies in ferromagnets are pointed out. (author)

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No abstract available