Detection of Atmospheric Pollutant NO With the Method of Resonant-Enhanced Multiphoton Ionization

NO is one of the key substances of air pollution. This paper presents the use of the technique of resonant enhanced multi-photon ionization (REMPI) for NO ambient detection. NO is ionized by absorbing four photons and via A2Σ intermediate resonant state when use 452.4nm laser as radiation source. A physical model concerning the ionization process is presented. It is shown that the ion signal depends on laser character and the dynamic parameters of NO. Two-photon absorption and ionization cross section about the resonant state are obtained from the ion decay curve and the model. The detection limit of this work, which can reach 1.4 ppm, is determined by measuring the variation of the ion signal with the concentration of NO.