A Method to Obtain the Absorption Coefficient Spectrum of Single Grain Coal in the Aliphatic C–H Stretching Region Using Infrared Transflection Microspectroscopy

A method was developed to obtain the absorption coefficient spectrum of a grain of coal (as small as ^10–7) in the region of aliphatic and aromatic C-H stretching bands (2700–3200 cm⁻¹) using infrared transflection microspectroscopy. In this method, the complex refractive index n – ik was determined using an optimization algorithm with the Kramers-Kronig transform so that the calculated transflection spectrum from the Fresnel equation corresponded to the measured one. The obtained absorption coefficients were compared with the bulk values determined from the potassium bromide (KBr) pellet measurement method.