Vibrational overtone spectroscopy of atmospheric organic chromophores .

摘要

This thesis presents studies of vibrational overtone spectroscopy and vibrational overtone chemistry. Vibrational spectra of four thiol molecules and two of their alcohol analogues are presented, with an emphasis on the SH- and OH-stretching overtones in the range of 1000 cm-1 -- 12000 cm-1. The relative strength of the SH-stretching vibrations in the fundamental region is found to be ∼0.2 as intense as the analogue alcohol OH-stretching vibration and ∼0.03 as intense in the first overtone. The small cross section of the SH-stretching overtone transitions is shown to result from low anharmonicity of the vibrational mode. Vibrational spectra and absorption cross sections are presented for vinylacetic acid, in the range of 1000 cm-1 -- 16500 cm-1, obtained using Fourier Transform infrared spectroscopy and cavity ring down spectroscopy. Ab initio calculations are presented to determine the thermodynamic threshold to reaction of vinylacetic acid.