Method for measuring concentration of nitrogen dioxide in air by single-wavelength laser induced fluorescence method, and apparatus for measuring concentration of nitrogen dioxide by the method
First Claim
1. An atmospheric nitrogen dioxide concentration determining method by a single-wavelength laser induced fluorescence technique, characterized in that it comprises the steps of:
- sampling a test atmosphere from an ambient atmosphere containing nitrogen dioxide of which a concentration is as low as in the pptv order of magnitude and providing a reference atmosphere from the test atmosphere by removing nitrogen dioxide therefrom;
irradiating each of the test atmosphere and the reference atmosphere with a single-wavelength laser light having an energy of exciting a nitrogen dioxide molecule from its ground state 2A1 to its excited state 2B2;
measuring intensity of a light emitted from the test atmosphere and intensity of a light emitted from the reference atmosphere; and
subtracting the intensity of the light emitted from the reference atmosphere from the intensity of the light emitted from the test atmosphere to determine the concentration of nitrogen dioxide in the test atmosphere which is as low as in the pptv order of magnitude.
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Abstract
A method and apparatus for measuring the concentration of a trace nitrogen dioxide contained in the atmosphere on a pptv level with excellent accuracy by a single-wavelength laser induced fluorescence method. The device comprises a laser light source unit, a light excitation unit, a light guide unit, an air passing unit for passing either the air to be measured or a reference air prepared by removing nitrogen dioxide from the air to be measured, a light sensor unit and a control unit. A single-wavelength laser beam is applied to the air to be measured and the reference air. The intensity of the light emitted from the air to be measured and the intensity of the light emitted from the reference air are measured, and the concentration of nitrogen dioxide is determined by using the difference between the two.
9 Citations
19 Claims
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1. An atmospheric nitrogen dioxide concentration determining method by a single-wavelength laser induced fluorescence technique, characterized in that it comprises the steps of:
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sampling a test atmosphere from an ambient atmosphere containing nitrogen dioxide of which a concentration is as low as in the pptv order of magnitude and providing a reference atmosphere from the test atmosphere by removing nitrogen dioxide therefrom; irradiating each of the test atmosphere and the reference atmosphere with a single-wavelength laser light having an energy of exciting a nitrogen dioxide molecule from its ground state 2A1 to its excited state 2B2; measuring intensity of a light emitted from the test atmosphere and intensity of a light emitted from the reference atmosphere; and subtracting the intensity of the light emitted from the reference atmosphere from the intensity of the light emitted from the test atmosphere to determine the concentration of nitrogen dioxide in the test atmosphere which is as low as in the pptv order of magnitude. - View Dependent Claims (2, 3, 19)
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4. An atmospheric nitrogen dioxide concentration determining apparatus implementing a single-wavelength laser induced fluorescence technique, characterized in that it comprises:
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a pulsed single-wavelength laser light source means for generating a pulsed laser light of a wavelength having an energy of exciting a nitrogen dioxide molecule from its ground state 2A1 to its excited state 2B2; a photoexciting means for passing the pulsed laser light from the pulsed single-wavelength laser light source means through atmospheric air to excite the atmospheric air; a light lead-in means for guiding the pulsed laser light into said photoexciting means; an atmosphere conducting means for guiding each of a test atmosphere and a reference atmosphere having nitrogen dioxide removed from the test atmosphere by passing the test atmosphere through a diffusion scrubber in the form of a tube having a tube wall coated with powdery titanium dioxide, selectively to said photoexciting means; a light detecting means for measuring intensity of a light emission produced in said photoexciting means; and a control means for controlling the time sequence of operations of said pulsed laser light source means and said light detecting means and also processing detection signals issued from said light detection means to display a processing result, whereby a concentration of nitrogen dioxide in said test atmosphere is determined which is as low as in the pptv order of magnitude. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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Specification