Uses and Techniques
Photoacoustic spectroscopy has become a powerful technique to study concentrations of gases at the part per billion or even part per trillion levels. Modern photoacoustic detectors still rely on the same principles as Bell’s apparatus, however to increase the sensitivity the following modifications have been made:
- Use of intense lasers instead of the sun to illuminate the sample since the intensity of the generated sound is proportional to the light intensity; this technique is referred to as "laser photoacoustic spectroscopy" or "LPAS"
- The ear has been replaced by sensitive microphones. The microphone signals are further amplified and detected using lock-in amplifiers.
- By enclosing the gaseous sample in a cylindrical chamber, the sound signal is amplified by tuning the modulation frequency to an acoustic resonance of the sample cell.
Read more about this topic: Photoacoustic Spectroscopy
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