Advantages of AOTF-Based Spectrometers Application in Ambient Air Monitoring

Advantages of long-path absorption spectrometers based on acousto-optical tunable filters (AOTF) in ambient air monitoring are considered.

Characteristic features of long-path spectroscopic technique are analysed. There are formulated their advantages in comparison with local (contact) methods. The spectroscopic techniques are preferable due to ability to monitor large-scale air masses in real time in natural conditions and also they make sampling and sample preparation unnecessary. Moreover, long-path approach allows to increase an accuracy due to elimination effects of temporal and spatial fluctuations of air.

Beside these general methodological advantages, AOTF-based spectrometers ensure some specific extra preferences in gas analyses. Key advantage is the random-spectral-access measurement procedure. As numerical characteristic of the advantage factor, time-saving ratio - T, is suggested. It is derived an analytical expression which relates advantage factor to numeric physical characteristics of instruments and of objects being investigated. Computations manifest significant (10-1000 times) reduction of required detection time in comparison with scanning spectrometers based on diffraction gratings.