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2 February 2009 Time decay spectrum and the fluorescence detection of NO2
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The fluorescence lifetime of the excited NO2 molecules are observed experimentally by the technique of LIF time decay spectrum. The results show that the time decay spectrum presents a property of bi-exponential. This indicates that the fluorescence is composed of two components. One has a long lifetime, while the other has a short one. The short-lived component comes from the radiation of the molecules excited by B2B1←X2A1 transition. And the long one is owing to the radiation of the molecules excited to the high rovibronic levels of the ground electronic state. These levels are correlated with A2B2 state. The deactivation mechanism of the excited molecules is investigated by measuring the variation of fluorescence lifetime versus the sample pressure. The conclusion is that the excited molecules that corresponding to the short lifetime quench mainly by the process of radiation and fast inner conversion. As to the excited molecules with long lifetime, the deactivation process is not only radiation, but also the non-radiation process of collision. At the same time, the optimum-receiving wavelength of 630nm for detection NO2 gas with the technique of LIF is proposed by measuring the dispersive spectrum. Under the condition of standard atmosphere, a detection limit of 6ppb is obtained with the experimental apparatus.
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Guiyin Zhang and Yidong Jin "Time decay spectrum and the fluorescence detection of NO2", Proc. SPIE 7160, 2008 International Conference on Optical Instruments and Technology: Optoelectronic Measurement Technology and Applications, 71600B (2 February 2009);


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