Thesis (M.Sc.)--Chulalongkorn University, 2001

A good contact between a sample and ATR prism is crucial for attenuated total reflection Fourier transform infrared spectroscopy. If a good contact is not achieved, there is an air gap between the solid sample and the IRE. This research studied the influence of the air gap. The air gap affects the absorbance of the sample. The greater air gap, the smaller the absorbance, especially for solid sample with rough surface. The greater is the roughness, the smaller is the absorbance. In this research, a technique for enhancing absorbance of the solid sample is developed. By replacing the air gap with a liquid of similar refractive index to that of the sample, absorbance of the solid sample in liquid assisted-system contact is significantly improved. Moreover, a technique for calculating the bulk spectrum of the solid sample from observed spectra is proposed. The accurate bulk spectrum can be obtained under small absorption condition. Applicability of these techniques has been theoretically and experimentally verified.