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Generalized quantum defect methods in quantum chemistry

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dc.contributor.advisor Robert W. Field. en_US Altunata, Serhan en_US
dc.contributor.other Massachusetts Institute of Technology. Dept. of Chemistry. en_US 2008-02-12T16:50:47Z 2008-02-12T16:50:47Z 2006 en_US 2006 en_US
dc.identifier.uri en_US
dc.description Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2006. en_US
dc.description Vita. en_US
dc.description Includes bibliographical references (p. 247-254). en_US
dc.description.abstract The reaction matrix of multichannel quantum defect theory, K, gives a complete picture of the electronic structure and the electron - nuclear dynamics for a molecule. The reaction matrix can be used to examine both bound states and free electron scattering properties of molecular systems, which are characterized by a Rydberg/scattering electron incident on an ionic-core. An ab initio computation of the reaction matrix for fixed molecular geometries is a substantive but important theoretical effort. In this thesis, a generalized quantum defect method is presented for determining the reaction matrix in a form which minimizes its energy dependence. This reaction matrix method is applied to the Rydberg electronic structure of Calcium monofluoride. The spectroscopic quantum defects for the ... states of CaF are computed using an effective one-electron calculation. Good agreement with the experimental values is obtained. The E-symmetry eigenquantum defects obtained from the CaF reaction matrix are found to have an energy dependence characteristic of a resonance. The analysis shows that the main features of the energy-dependent structure in the eigenphases are a consequence of a broad shape resonance in the 2E+ Rydberg series. en_US
dc.description.abstract (cont.) This short-lived resonance is spread over the entire 2E+ Rydberg series and extends well into the ionization continuum. The effect of the shape resonance is manifested as a global "scarring" of the Rydberg spectrum, which is distinct from the more familiar local level-perturbations. This effect has been unnoticed in previous analyses. The quantum chemical foundation of the quantum defect method is established by a many-electron generalization of the reaction matrix calculation. Test results that validate the many-electron theory are presented for the quantum defects of the lsagnpo, E+ Rydberg series of the hydrogen molecule. It is possible that the reaction matrix calculations on CaF and H2 can pave the way for a novel type of quantum chemistry that aims to calculate the electronic structure over the entire bound-state region, as opposed to the current methods that focus on state by state calculations. en_US
dc.description.statementofresponsibility by Serhan Altunata. en_US
dc.format.extent 254, [1] p. en_US
dc.language.iso eng en_US
dc.publisher Massachusetts Institute of Technology en_US
dc.rights M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. en_US
dc.rights.uri en_US
dc.subject Chemistry. en_US
dc.title Generalized quantum defect methods in quantum chemistry en_US
dc.type Thesis en_US Ph.D. en_US
dc.contributor.department Massachusetts Institute of Technology. Dept. of Chemistry. en_US
dc.identifier.oclc 77279368 en_US

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