Spectroscopic and theoretical studies of small molecules.

Ferguson, Allan M.

Abstract

This thesis is concerned with two contrasting molecules - ketene (H2CCO) and methylene chloride (CH2CI2). High resolution (~0.05cm-1) infrared studies of ketene were carried out and complete analyses performed to the A1 species vibrations v1-v4, allowing the determination of revised vibrational frequencies and rotational parameters. Perturbations found to be present in all bands were elucidated and identified with the aid of H2C13CO, H213CCO and D2CCO isotopic species. Approximate analyses on these species also permitted the determination of revised D2CCO A1 vibrational frequencies and 13C frequency shifts. Preliminary analyses were also performed to the two B1 species vibrations, v5 and v6, and two of the three B2 vibrations, v7 and v8 in order to determine precise 13C frequency shifts for use in force field calculations. Subsequent empirical harmonic force field studies for ketene were carried out and 16 out of 19 force constants were determined. Owing to inaccuracies in a large number of the A1 vibrational frequencies and shifts arising through perturbations, the corresponding force constants were poorly defined. Complementary and supplementary ab initio force field studies were also carried out. The well-defined empirical constants were found to be in excellent numerical agreement with their corresponding ab initio values. For the inadequately described empirical CH2 symmetric stretch interaction constants, the ab initio values were preferred, and were included in what is considered to be the best compromise force field for ketene, in the absence of accurate unperturbed data. Empirical force field studies of methylene chloride suffered none of the set-backs encountered for ketene and thus a complete set of accurate force constants was determined. Complementary ab initio force field studies were carried out and found to be in good overall agreement with those of the empirical studies.

Citation

FERGUSON, A.M. 1986. Spectroscopic and theoretical studies of small molecules. Robert Gordon's Institute of Technology, PhD thesis. Hosted on OpenAIR [online]. Available from: https://doi.org/10.48526/rgu-wt-1993270

• Thesis Type: Thesis
• Deposit Date: Aug 7, 2024
• Publicly Available Date: Aug 7, 2024
• DOI: https://doi.org/10.48526/rgu-wt-1993270
• Public URL: https://rgu-repository.worktribe.com/output/1993270
• Award Date: Dec 31, 1986