Gas analysis by a Stark-sweep microwave cavity spectrometer

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Other Title
  • シュタルク掃引マイクロ波空どう分析計によるガス分析
  • シュタルク ソウイン マイクロハ クウドウ ブンセキケイ ニヨル ガス ブンセ

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Abstract

A K-band microwave cavity spectrometer of a Stark-voltage sweep type was constructed as a pollutant monitor. The spectrometer incorporated a Gunn effect microwave oscillator and a microwave bridge of magic-T. A gas absorption cell was a TE1, 0, nmode rectangular cavity resonator in which an internal Stark electrode was installed. Internal dimension of the resonant cavity is 6.5 mm in height, 13 mm in width and about 800 mm in length. The resonator was attached to an arm of magic-T. Spectrum of pollutant gas was obtained by continuous sweep of the Stark dc voltage supplied to the internal electrode. These devices made the spectrometer compact and highly sensitive. Various pollutant molecules which had electric dipole moment were detected at the concentration around a few hundreds ppm. These were sulfur dioxide, ammonia, acrolein and dimethyl sulfide. Specially, 0.2 ppm ammonia in nitrogen was detected. Dependence of peak absorption intensity on sample pressure was discussed. A calibration curve for ammonia in nitrogen base-gas showed good linearity in the concentration from 1 to 10 ppm under conditions that the oscillating frequency and the total sample pressure were 23.875 GHz and 0.8 Torr, respectively.

Journal

  • BUNSEKI KAGAKU

    BUNSEKI KAGAKU 28 (9), 544-549, 1979

    The Japan Society for Analytical Chemistry

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