1. From photophone to photoacoustics
Photoacoustic detection involves exciting molecules with light and then detecting their non-radiative de-excitation using an acoustic microphone. The technique is far from new, dating back to 1880, when Alexander Graham Bell discovered this effect in solids and, later, in gases. The process was forgotten and then rediscovered with the invention of the microphone in the 1930s and the laser in the 1970s.
Photoacoustic measurement methods are finding increasing application in spectrometry and in the study of the interaction of light with matter. The photoacoustic effect consists in the formation of acoustic waves in a sample periodically illuminated by light. The origin of this effect is explained by non-radiative transitions transforming part of the energy of the absorbed radiation into thermal energy which, under certain conditions, gives rise to acoustic vibrations....
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From photophone to photoacoustics
Overall principle
Manufacturers – Suppliers – Distributors
Omnisens Systems (Switzerland) http://www.omnisens.ch/
Omnisens trace gas analyzers combine photoacoustic spectrometry with an innovative, highly sensitive detection technique. This results in fast response times, low detection limits and operation without periodic recalibration. The TGA320-X device detects ammonia (NH 3 ) for applications...
Bibliography
Websites
University of Reims. http://www.univ-reims.fr/
Harvard University. http://cfa-www.harvard.edu/HITRAN/
Alpes lasers. http://www.alpeslasers.com/...
Theses
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