| 摘要 |
A method of and apparatus for determining a concentration of nitrogen dioxide that is contained as a trace constituent in atmospheric air utilizes a single-wavelength laser induced fluorescence technique whereby a nitrogen dioxide concentration as lows as at a pptv level can be determined conveniently and accurately. The determination apparatus comprises a pulsed laser light source section (1), a photoexciting section (3) for exciting atmospheric air by passing therethrough a pulsed laser light (2) from the pulsed laser light source section (1), a light lead-in unit (4) for guiding the pulsed laser light (2) into the photoexciting section (3), an atmosphere conducting section (7) through which each of a test atmosphere (5) and a reference atmosphere (6) having nitrogen dioxide removed from the test atmosphere (5) is conducted selectively, a light detecting section (8) for measuring the intensity of a light emission generated in the photoexciting section (3), and a timing control section 9 whereby the time sequence of operations of the pulsed laser light source section (1) and the light detecting section (8) is controlled and detection signals issued from the latter are processed to display a result of the processing. Each of the test atmosphere (5) and the reference atmosphere (6) having nitrogen dioxide removed from the test atmosphere (5) is irradiated with a single wavelength laser light (2) to measure the intensity of a light emitted from the test atmosphere (5) and the intensity of a light emitted from the reference atmosphere (6), and the intensity of the light emitted from the reference atmosphere (6) is subtracted from the intensity of the light emitted from the test atmosphere (5) to determine the concentration of nitrogen dioxide in the test atmosphere. The reference atmosphere (6) is formed by passing atmospheric air (20) through a diffusion scrubber (19) having its tube wall coated with powdery titanium oxide (23).
|
