Near-Infrared Spectroscopy

The near-infrared portion of the electromagnetic spectrum is located between the visible and mid-range infrared (MIR) sections, roughly 750–2500 nm or 13,333–4000 cm 1 (see Fig. 6.1). It consists (mainly) of overtones and combinations of the bands found in the mid-range infrared region (4000–200 cm ). The region was discovered by Sir William Herschel in 1800 [1]. Sir William was attempting to discover the color of light that carried the heat of sunlight. He used a glass prism to split the colors from white light and arranged a series of thermometers, wrapped in dark cloth, such that they would each be exposed to a different colored light. Not much happened in the visible region, but as he allowed the thermometer to be located next to the red band, he noticed a dramatic