| 摘要 |
An infrared laser absorption spectrometer is disclosed wherein a pair of detector cells are disposed in series relative to the laser beam path, such beam path preferably being within the optical cavity of the laser. The laser beam is modulated to produce a modulation of the absorption, if any, by the sample materials in the two cells. Modulated absorption by the sample or samples produces an acoustic wave in each cell which is detected by a suitable microphone and subtracted so as to produce a difference signal corresponding to the difference in absorption between the two cells so that undesired background effects are cancelled, such as window heating, absorption by a carrier gas or the like which is common to both cells. A mirror placed over one end of one of the cells allows a two cell optoacoustic detector geometry having only two windows therein. The dual optoacoustic cell is particularly useful for monitoring the output of a gas chromatograph since the background associated with the carrier stream can be cancelled.
|
