Overtones are higher-order molecular vibrations that occur at multiples of a fundamental vibrational frequency. In near-infrared (NIR) spectroscopy, overtone absorptions are much weaker than the corresponding fundamental absorptions observed in the mid-infrared region, allowing NIR light to penetrate deeper into many materials.
Most NIR analytical methods rely on overtone bands of C-H, O-H, and N-H chemical bonds to measure moisture, fats, proteins, oils, and other organic constituents in agricultural, food, pharmaceutical, and industrial applications.
