[A method of eliminating the water vapor interference simultaneously in open path FTIR measurement by instrumental...

Water vapor absorption, which exists in mid-infrared region, is an interferential element for infrared spectra analysis. A new method, which can be used to eliminate the water vapor interference in FTIR measurement, is presented. To calculate the high resolution absorbance of water vapor, a fast line by line method which computed with the HITRAN database (eg. line strength, self broadening, air broadening, etc) and meteorological parameters (eg. temperature, pressure, and relative humidity) was used. After convolving with Instrumental line shape (eg. divergence angle, resolution, etc), the absorbance of water vapor was then transferred from high resolution to low resolution, which matched the instrumental parameters. After the acquirement of water vapor absorbance spectrum, it will be subtracted from the measured spectrum to calculate the spectrum with the water vapor was eliminated. In the present work, analysis of measured data from open path FTIR is described. Only the absorbing character and noise was left in the spectrum after eliminating the water vapor interference. Consequently, this method has an ideal effect on water vapor elimination when there is no dryer can be used, especially in the case of open path FTIR measurement.