Calculated Potential Energy Surfaces and Vibrational Analysis

University dissertation from Department of Theoretical Chemistry, Lund University

Author: Niclas Forsberg; Lunds Universitet.; Lund University.; [2001]

Keywords: NATURVETENSKAP; NATURAL SCIENCES; Benzene; HCO; NEMO; Imaginary Level Shift; Double Harmonic Approximation; Potential Energy Surface; CASPT2; Franck-Condon Factors; CASSCF; p-Benzosemiquinone; Theoretical chemistry; quantum chemistry; Teoretisk kemi; kvantkemi;

Abstract: The focus of this thesis is on the calculation of potential energy surfaces and on the study of vibrational properties. For example: - We have developed a new method for calculation of Franck-Condon factors. - We have calculated full energy surfaces of the ground (X2A’) the excited (B2A’) states of the formyl radical. These surfaces have been used to study the hydrocarbon flame bands of the B2A’ <- X2A’ transition. - We have used the double harmonic approximation to vibrationally resolve the transitions to the lowest valence states in the benzene spectrum. - We have developed an imaginary level shift method used to eliminate singularities in the multiconfigurational perturbation method, CASPT2. The results of these calculations have been compared to and discussed in relation to other theoretical calculations and/or to experimental results.

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