SPECIFIC CHEMICAL SPECIES DETECTING METHOD AND CHEMICAL SPECIES DETECTING DEVICE

PURPOSE:To improve the S/N ratio of a specific chemical species so as to enable detection of high sensitivity by making detected light differ from the band of exciting light so as to eliminate the influence of scattered light generated in association with the exciting light. CONSTITUTION:A photomultiplier 10C is provided at an angle of 45 deg. to the optical axis of laser beams 5, and an image emphasizing device 11b and a CCD camera 2 are provided at an angle of 90 deg.. Band-pass filters 3a, 3b centering around detected wavelength are installed at the detecting parts of the photomultiplier 10C and image emphasizing device 11b, and the signals of the photomultiplier 10C are computed by a boxcar integrator 10d to perform excitation scanning. In the detection of a specific chemical species, the wavelength of exciting laser beams to be used and the transmission band of fluorescence received by a light detecting device 2 serving as a detecting means are determined by selecting the wavelength band of the filter 3. In a chemical species CN, for instance, an absorption band near 357nm is excited, and fluorescence near 386nm is caught to detect CN so as to enable detection in the extremely high state of S/N.