Intensity, frequency and relaxation time in the carbon-hydrogen stretch overtones

This thesis comprises three investigations, each into a different aspect of the CH stretch overtone vibrations.; The first project was to investigate the intensity of some overtone vibrations. Trimethyl amine was chosen for the subject of this study. Trimethyl amine is of particular interest because it exhibits the largest known difference in CH bond lengths within a methyl group. This is due to what is known as the lone pair trans effect. Dimethyl sulfide also exhibits the lone pair trans effect but to a far lesser extent making it ideal for comparison to trimethyl amine. In this part, the first through fourth overtone spectra of N(CH3)3, N(CD3) 3, N(CD2H)(CD3)2, N(CH3)(CD 3)2, N(CD3)(CH3)2 and S(CH 3)2 are reported. Tentative assignments are offered for all of the major bonds observed. The intensities of the observed bands are compared to predicted intensities calculated using the harmonically coupled anharmonic oscillator local mode (HCAO LM) model. Results of these experiments have shown good correlation between the experimental and predicted intensities. As well, some evidence that the lone pair produces increased coupling between methyl groups has been observed.; The second project investigated the energy of CH stretch overtone bands of metallocenes. The first through third overtone spectra of ferrocene, ruthenocene, nickelocene, cobaltocene, dicyclopentadienyl magnesium and sodium cyclopentadienyl are examined with particular attention to the CH stretching of the cyclopentadienyl. From semi-empirical correlations between CH bond length and CH stretching frequencies in each overtone region, it was determined that the type of metal atom within a metallocene complex has little effect on the CH bond length in the cyclopentadienyl. The only exception is cobaltocene where there is evidence that the Jahn-Teller effect results in several different CH bond lengths. Evidence that bis(cyclopentadienyl) magnesium is not ionic has been observed.; In the third project, a novel system based on photo acoustic spectroscopy was developed to measure the Vibrational-Translation relaxation rate of overtone vibrations. This is a subject of great interest as very little information exists on this process. The instrument developed here is termed Intra Cavity Laser Photo Acoustic Referenced Phase Shift (ICL-PARPS). This system relies on the tungsten wire within the cell to act as a reference so that accurate phase shifts can be measured. This allows for a Helmholtz resonator cell to be used to amplify the signal. This research serves as a feasibility study on the ICL-PARPS system. Some ambiguity still exists in the interpretation of the data collected and error in the values of the relaxation times found are still quite high. However, Vibrational-Translation relaxation times ate reported for several overtone vibrations of trimethyl amine and an overtone vibration of methane. It is hoped that further development into this technique will lead to advances in overtone spectroscopy.