Traditionally, near–IR or UV–Visible spectroscopy have not been widely used for gas analysis due to low sample density and the relative weakness of the overtone bands. However, this situation has changed dramatically with the advent of highly sensitive spectrometers such as those based on tunable diode lasers. This development provides two important benefits—a very significant increase in source brightness and the potential for high resolution. The latter benefit greatly enhances specificity and sensitivity by enabling the resolution of individual rotational bands.
FFT Series Gas Cells employ a folded–path design utilizing small diameter gold–coated lightguides. This design provides extremely low volume and rapid sample exchange. In addition, the precise overlap of the gas flow and optical paths insures a very high degree of stability and photometric accuracy. These cells are available in pathlengths to two meters.
FFM Series cells7 were designed primarily to meet the rigorous requirements of process gas analysis. These cells take advantage of the spatial coherence characteristic of the new generation of spectrometers based on tunable lasers to provide multiple pass operation combined with ease of alignment. In addition, the mirror coatings are on the outside of fused silica windows, making it possible to completely clean out the cell without risking damage to the optics.