Development of Fourier transform spectrometry for UV-visible differential optical absorption spectroscopy measurements of tropospheric minor constituents
Ac. Vandaele et M. Carleer, Development of Fourier transform spectrometry for UV-visible differential optical absorption spectroscopy measurements of tropospheric minor constituents, APPL OPTICS, 38(12), 1999, pp. 2630-2639
Concentration measurements of trace gases in the atmosphere require the use
of highly sensitive and precise techniques. The UV-visible differential op
tical absorption spectroscopy technique is one that is heavily used for tro
pospheric measurements. To assess the advantages and drawbacks of using a F
ourier transform spectrometer, we built a differential optical absorption s
pectroscopy optical setup based on a Bruker IFS 120M spectrometer. The char
acteristics and the capabilities of this setup have been studied and compar
ed with those of the more conventional grating-based instruments. Two of th
e main advantages of the Fourier transform spectrometer are (1) the existen
ce of a reproducible and precise wave-number scale, which greatly simplifie
s the algorithms used to analyze the atmospheric spectra, and (2) the possi
bility of recording large spectral regions at relatively high resolution, e
nabling the simultaneous detection of numerous chemical species with better
discriminating properties. The main drawback, on the other hand, is due to
the fact that a Fourier transform spectrometer is a scanning device for wh
ich the scanning time is small compared with the total measurement time. It
does not have the signal integration capabilities of the CCD or photodiode
array-based grating spectrographs. The Fourier transform spectrometer ther
efore needs fairly large amounts of light and is limited to short to medium
absorption path lengths when working in the UV. (C) 1999 Optical Society o
f America.