Enhancement on sensitivities and selectivities of absorption and fluorescence spectrometries with combination of various optical effects and application to the natural water analysis.

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Various optical effects obtained with lights such as lasers have been used for enhancement in sensitivity and selectivity of absorption and fluorescence spectrometries. First, thermal lensing effect was investigated in the liquid crystal system. It has been discovered, when a dual beam system was employed, the focus of the thermal lens varied according to the orientation of the polarization plane of the probe laser. The thermal lensing signal is twice or larger than that in the isotropic media. Second, when polarized laser light was irradiated into the solution in which diluted magnetic fluid was coexistent with dye, fluorescence of the dye changes under magnetic field. It was found that the magnitude of this change depends on the molecular structure of the dye. These phenomena can be explained by orientation of the dye molecules to the magnetic fluid particles under magnetic field. These results show the oriented media are effective to improve the sensitivity and selectivity of absorption and fluorescence spectrometries. As the application of the optical effects, the photochemical characterization of dissolved organic matter in natural waters was carried out as to the multi-photon ionization. Dissolved organic matter was irradiated by 355 nm output of YAG laser for producing hydrated electrons. Life-time and quenchers of the generated hydrated electron are much different between seawater and land water. Photo-reduction of nitrate to nitrite and chemiluminescence of silane were also investigated for analyzes of nitrate and silicate in seawater.