In-Situ Laser Detection for Aerosols and Toxic Chemicals associated with Aerosols

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In this study, it was proved that laser breakdown causes through two main ionization mechanisms. One is multiphoton ionization, and the other is cascade ionization. From the breakdown of N_2 gas, it was founded that at low laser energy (<20mJ〜30mJ/pulse), cascade ionization effect was small, and multiphoton ionization effect was relatively large, and that at high laser energy(>20mJ〜30mJ/pulse), cascade ionization was main a mechanism. Introducing aerosols into N_2 gas led to promoting of cascade ionization of N_2 That is because of electrons produced on aerosols. Emission intensity from breakdown plasmas of Eu adsorbed on TiO_2 aerosols was founded to be larger than that of Eu existing freely from TiO_2. This is because of the size of aerosols. It is known that breakdown probability increases with the size of aerosols. On the other hand, the intensity of Ti I decreased as the amount of adsorbed Eu increased, meaning that TiO_2 was breakdowned by cascade ionization induced by electrons from adsorbed Eu.Furthermore, the particles were completely dispersed in aqueous solutions and the realization of breakdown spectroscopic technique was validated by using the natural environmental waters. It was confirmed that the technique is useful for In-Situ quantitative detection of aerosols/dispersed particles in atmosphere and in environments and of toxic chemicals especially heavy metals associated with aerosols and particles.