Development of a measurement system for nitrate radical and dinitrogen pentoxide using a thermal conversion/laser-induced fluorescence technique
- Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan and Department of Applied Chemistry, Faculty of Engineering, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397 (Japan)
An instrument for measuring atmospheric nitrate radical (NO{sub 3}) and dinitrogen pentoxide (N{sub 2}O{sub 5}) has been developed by a thermal conversion/laser-induced fluorescence (TC/LIF) technique. N{sub 2}O{sub 5} is thermally decomposed and converted to NO{sub 3}, which is measured by laser-induced fluorescence. In situ, fast-response, sensitive measurement of NO{sub 3}/N{sub 2}O{sub 5} is expected by use of LIF. In detecting NO{sub 3}, dual-wavelength excitation at 622.96 and 618.81 nm was adopted to remove potential interference and to guarantee high selectivity. A high-power dye laser system was used as the source of excitation light. To measure ambient air directly, the NO{sub 3} detection cell was placed on the rooftop. The laser beam was guided by an optical fiber into the excitation cell. Transmittance of the laser beam was 80% for a 10 m long fiber. To calibrate the instrument, the series of thermal decomposition of N{sub 2}O{sub 5} and the gas phase titration of NO{sub 3} by NO were conducted. NO{sub 3} reduction by adding NO was also applied to determine accurately the zero points of the detector. After optimization of conditions such as gate timing in photon counting and the settings of the N{sub 2}O{sub 5} converter, the present detection limits of NO{sub 3} and N{sub 2}O{sub 5} were determined to be 4 and 6 pptv, respectively, for the integration time of 10 min (signal-to-noise ratio=1). It was confirmed that the interference of NO{sub 2} on N{sub 2}O{sub 5} detection is negligible, but can be significant for NO{sub 3} measurement when NO{sub 2} concentration is extremely high (>100 ppbv). Measurement of N{sub 2}O{sub 5} in ambient air was made in the urban area of Tokyo, Japan. Observed data demonstrated the capacity of the TC/LIF instrument with a powerful dye laser and a single-path excitation cell for ambient measurements. In this article, we focus on the instrumentation and characterization.
- OSTI ID:
- 20722913
- Journal Information:
- Review of Scientific Instruments, Vol. 76, Issue 6; Other Information: DOI: 10.1063/1.1927098; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
- Country of Publication:
- United States
- Language:
- English
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