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In order to estimate photodissociation rates of atmospheric trace gases at several altitudes, photoabsorption cross sections of these compounds have been measured in the ultraviolet region. The cross sections obtained show a temperature effect in the wavelength region longer than 200nm. The cross sections for CFC-112, CFC-113, and CFC-114 change through the substitution between Cl and F atoms among these molecules. Photodissociation rates were estimated using the observed cross section data and the calculated solar radiation intensities from the literature data. The life times for these molecules as well as CFC-12, CFC-13, and HCFC-123 are found to be longer than 105 years at the altitude of 10km, and those for CFC-113 and HCFC-123 are about 100 years at 20km. An infrared-ultraviolet double resonance laser-induced fluorescence method has been developed for observation of the OH radical in the troposphere, which exists in extremely low concentrations like 106 molecules/cm3 , but plays a critical role in the atmospheric chemistry. The detection limit of this technique was experimentally determined and the monitoring in the atmospheric environment is discussed. A method for the selective detection of alkyl isomer radicals has been developed by using photo-ionization mass spectrometry. Site selectivities in reactions of O/OH+alkans and of O2 with butyl radicals were investigated using this method.
Photoabsorption Cross Section, IR-UV LIF Method, OH Concentration, Photoionization Mass Spectrometry, Alkyl Peroxy Radicals