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dc.contributor.advisorRittby, C. Magnus L.
dc.contributor.authorGarcia, Guillermoen_US
dc.date.accessioned2014-07-22T18:47:20Z
dc.date.available2014-07-22T18:47:20Z
dc.date.created2008en_US
dc.date.issued2008en_US
dc.identifieretd-08132008-110703en_US
dc.identifiercat-001400982en_US
dc.identifier.urihttps://repository.tcu.edu/handle/116099117/4061
dc.description.abstractComparisons between theoretical predictions and experimental measurements of vibrational fundamentals and isotopic shifts represent a method for the identification of new molecular species. For molecules with near-lying vibrational fundamentals, experimental and theoretical factors complicate the interpretation of isotopic spectra where isotopic shift measurements are recorded. Experimentally, a large number of absorptions in a small region of the spectrum are observed. Theoretically, two factors affect the calculation of isotopic shifts in the harmonic approximation: i) the sensitivity of the calculations due to the interaction of vibrational fundamentals and ii) the sensitivity of the calculations due to the anharmonicity of the interaction potential. The study of vibrational spectra of long carbon chains exhibits these problems.^The present work is an investigation of the theoretical issues that affect the calculations.^As a consequence of this investigation, two theoretical methods were developed in the framework of perturbation theory in order to aid in the interpretation of isotopic spectra of homonuclear molecules. Both theoretical methods are presented in this work. The first method, called the isotopic deperturbation method, is introduced in order to aid dealing with the complications regarding the sensitivity of simulated spectra due to the interactions of vibrational fundamentals. The second method is introduced here in order to estimate the anharmonicity of vibrational fundamentals from isotopic shift measurements.^The isotopic deperturbation method is applied to the infrared isotopic spectra of linear Cn (n = 3 - 12, 15, 18) and confirms our hypothesis regarding the high sensitivity of the isotopic shift calculation for molecules with near-lying vibrational fundamentals.^The method to calculate anharmonic contributions is applied to the experimental spectra of linear carbon chains C2n+1 , n=1-5 as well as to cyclic C6 and C8; the results are compared with the calculated anharmonicity using a density functional theory (DFT) perturbative approach and existing calculations in the literature.
dc.format.mediumFormat: Onlineen_US
dc.language.isoengen_US
dc.publisher[Fort Worth, Tex.] : Texas Christian University,en_US
dc.relation.ispartofTexas Christian University dissertationen_US
dc.relation.ispartofUMI thesis.en_US
dc.relation.requiresMode of access: World Wide Web.en_US
dc.relation.requiresSystem requirements: Adobe Acrobat reader.en_US
dc.subject.lcshVibrational spectra.en_US
dc.subject.lcshIsotope shift.en_US
dc.titleAn investigation into the limitations of the harmonic approximation in the calculation of vibrational isotopic shiftsen_US
dc.typeTexten_US
etd.degree.departmentDepartment of Physics and Astronomy
etd.degree.levelDoctoral
local.collegeCollege of Science and Engineering
local.departmentPhysics and Astronomy
local.academicunitDepartment of Physics and Astronomy
dc.type.genreDissertation
local.subjectareaPhysics and Astronomy
etd.degree.nameDoctor of Philosophy
etd.degree.grantorTexas Christian University


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