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gases, polluted the atmosphere

 

We have extensive experience in DOAS instruments design and implementation.  DOAS-M1 is a commercial DOAS spectrometer based on single coaxial telescope scheme. The instrument is described in more detail here: (PDF, 240KB).

Analysis of measurements of gaseous pollutants by DOAS-4R gas analyzer is given here: (PDF,146kB) .

Differential Optical Absorption Spectroscopy (DOAS)

is a method of retrieval of column abunadancies of atmospheric trace-species from measurements of electromagnetic radiation in a specified spectral interval.The retrieved DOAS quantity is derived from two absorption spectra: one in which the light has passed through little of the absorber in question and one in which the light has passed though a large amount of the absorber. 

DOAS Advantages

  • High sensitivity, detection of very low density levels ( of units of ppbv) is possible;
  • Real-time measurements;
  • Simultaneous measurements of up to 30 trace species;
  • Measurements can be performed automatically;
  • Minimum maintenance;
  • No air samples required;
  • Self-calibrated system (a calibration cell is used);
  • Stationary and mobile versions are available

Instrument Control and  Data Analysis Software

The designed Windows software allows the user to configure the measurements (to change the averaging time and  spectral range, the scanning speed, to select the species), to observe measurement results as a chart on the monitor and to store them.

 DOAS block diagram

The radiation of the Xenon short arc lamp is passed by the transmitting channel  of the coaxial telescope through the open path (from 200 to 1000 meters long) toward the fused silica retroreflector and is reflected backward to the receiver (telescope). Then the light passes through the fiber optic guide to the monochromator and a spectrum is detected by the diode array.The spectrum is analyzed to determine the average concentration of the species in question by the computer.

The principle of DOAS operation

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