The excitation of light source is the important constituent of photoelectric direct reading spectrometer system, it takes on the material physical evaporation, dissociation and atomization and the other important constituent of the excitation, actually the analysis measured methods of several main technical indicators to be good or bad, such as the spectral analysis of the detection limit, the precision and the accuracy, to a great extent depends on the excitation of light source.
The Excitation of light source has two action processes. it is evaporated the samples and excited the atomic to produce spectrum. Both work at the same time and jointly determine the intensity of the spectral line. In the sample the element evaporatedand dissociated, will involve in the physical and chemical properties of the sample components.
Excited the vaporized atomic, related to the character of light generator, and more closely related to the generator electrical properties, so it can be said that the excitation of light source determines the spectral analysis method, so the understanding of light resource, it is needed for the spectral workers.
Due to the wide range of the spectral analysis samples, the shape sample was different, excitation of the elements with different difficult, It is very difficult to use a kind of excitation light source to meet the different tasks analysis.Therefore, each type of light source has its own characteristics and application scope, according to the different purpose of analysis and selection of different types of light source.
Consider From the quantitative analysis, the requirements of light source are as follows: highly analysis sensitivity and can analyze the trace, trace element, the sensitivity can up to ppm or ppb magnitude; high sensitivity of the concentrations, it means when there has minor changes with the analysis element content C, corresponding big changes in the analysis line 2, namely DI / DC;during the excitation process, the light source should have good stability and reproducibility, those basic requirements ensures the accuracy of the analysis;small matrix effects, the matrix content changes in the sample, the result are not affected by the changes of matrix effects. The Third elements of the impact and the impact of the organizational structure, the shape of samples has a small mass effect;about the burning time, exposure time (integral) should be short, that can improve the efficiency and the speed of analysis;Instrument has the advantages of simple structure, small volume, and easy operation, safe and reliable.
Because the power of spectrum analysis, using the photoelectric conversion measurement to instead the photosensitive plate measurement; the photometric error ≤ 0.2%, and the source of error in about 1%, playing a prominent role in the total spectrum error analysis, so using the photoelectric direct reading spectrometry, adopting the good performance of the excitation light source has a very important significance. The excitation light is used two electrode method; switch on the current, a light source is formed between electrodes. In this light source, the air (or gas) between the electrodes is in the atmospheric pressure. So the discharge occurred between the gas electrodes, is relying on the electrode current flowing through the gas to get light, which built on the basis of gas discharge.
Just like the low discharge pressure and the control wave source in the capacitor electric field, adopting the controlling atmosphere to discharge, but the glow light source is discharge by controlling the thin atmosphere under the action of DC electric field. The Plasma light source discharged in RF electromagnetic field by controlled atmosphere, it should be pointed out that, the voltage between the electrodes and the current relationship was not observed the Ohm’s law when the gas through the current.