Calculation technique of diffuse reflectance spectra using an ensemble of damped harmonic oscillators model for substances identification

We present the technique and experimental laboratory setup for measuring and analysis of diffuse reflectance spectra. The Experimental spectra obtained by tunable infrared quantum cascade laser with average power of 15 mW. Using causality relations for real and imaginary parts of reflectivity we can calculate the extinction coefficient. We use dumped harmonic oscillator (DHO) model to calculate synthetic spectra and test KramersKronig relations for spectra calculations. Using experimental setup and numerical methods of spectra analysis we could identify the diethyl phthalate (DEP). The proposed method can be used in routine laboratory analysis to complement the ATR and DRIFTS methods of IR spectroscopy.