ABSTRACT
Vibrational spectroscopy is concerned with the detection of transitions between energy levels in molecules that result from stretching and bending vibrations of the interatomic bonds. At room temperature most molecules exist in their ground vibrational states and in order to excite them to higher vibrational states energy must be absorbed. The two experimental techniques which are used to detect changes in vibrational energy states are infrared spectroscopy (IR) and Raman spectroscopy. IR in particular is used to investigate the chemical reactions of polymers including oxidation and environmental degradation, thermal degradation and pyrolysis, so important to understanding in-service behaviour of polymers. Raman spectroscopy is concerned with detection of light scattered inelastically by molecules interacting with incident monochromatic radiation. NearIR spectra arise from overtones of the fundamental vibrations and hence the technique is complementary to IR and Raman spectroscopy and is finding applications for a variety of process and analysis tools.
