The application of SIMS to sulfur dioxide detection

The operating principles, design and applications of a SIMS (French acronym for selective modulation interference spectrometer) apparatus for the detection of sulfur dioxide are discussed. The SIMS is presented as consisting of an interferometer projecting fringes onto a vibrating grating which causes the modulation of specific spectral bands while overcoming limitations imposed on conventional slit spectrometers by the constancy of their luminosity resolution product. The construction of an SO2 detector based on these principles employing an SO2 interferogram behind a parabolic mask in place of the grating to obtain the derivative correlation product of reference and experimental interferograms is described. Successful applications of the device, designed to operate in the spectral region surrounding the SO2 absorption band at 300 nm, for SO2 measurements in plumes, ambient air and industrial smoke stacks are presented, and possible application of SIMS to the regulation of sulfur cycles and the detection of other gases such as nitrogen oxides are indicated.