Study on non-dissociative bimolecular reactions characteristic of contact molecular pairs

臭氧-水复合体被认为是地球对流层中的羟基自由基源之一。与水蒸气的络合作用可能会改变O3光化学，这可能在羟基自由基的产生中起着关键作用。对O_3-H_2O络合物的光谱进行了表征。在本研究中，我们研究了臭氧-水在低温基质中的光化学行为。用Ne、Ar、氪作为基质介质，研究了所谓的基质笼子效应，并将固相化学发展为气相反应。用紫外光和可见光研究了光化学的波长依赖性，选择臭氧ν_3基区来监测臭氧单体和臭氧-水复合体中臭氧光解离的发生，因为臭氧-水复合体的ν_3基团与单体ν_3带完全分开。在霓虹灯基质中，355 nm辐射导致臭氧单体和臭氧水络合物减少，过氧化氢生成。显然，臭氧的光解离即使在355 nm处也能发生。在Ar和氪基质中也观察到了过氧化氢-水的络合物，认为它是由笼子中的O(^1D)原子与水二聚体在不同的笼子中发生的笼间反应而形成的。结果表明，由于笼间反应的存在，在氙气中过氧化氢的生成量几乎为1，而在氩和氪中的过氧化氢生成量超过1。我们认为，霓虹灯是研究臭氧-水复合体光化学最合适的介质。研究了固体霓虹灯的波长依赖性。在355 nm照射下，254 nm和313 nm照射得到了类似的结果，而365 nm和633 nm照射没有引起任何光化学反应。我们将讨论光化学机制(波长和基质笼的依赖性)以及大气臭氧化学的意义。

Ozone-water complex has been suggested as one of the hydroxyl radical sources in the Earth's troposphere. Complexation with water vapor might change the O_3 photochemistry, which might play a crucial role in the production of hydroxyl radical. We have characterized the spectroscopy of O_3-H_2O complex. In this research, the photochemistry of ozone-water complex isolated in cryogenic matrices was studied. Neon, argon, and krypton were employed as matrix media to study the so-called matrix cage effect and to develop the solid state chemistry to the gas phase reaction. Wavelength dependence of photochemistry was studied by using UV and visible light.Ozone ν_3 fundamental region was chosen to monitor the occurrence of ozone photo-dissociation within the monomer and ozone-water complex, because the ν_3 fundamental of the ozone-water complex was fully separated from the monomer ν_3 band. In a neon matrix, the irradiation by 355 nm led to the decreases of ozone monomer and ozone water complex and to the formation of hydrogen peroxide. Apparently the photo-dissociation of ozone was found to take place even at 355 nm. In argon and krypton matrices, the formation of hydrogen peroxide-water complex was also observed, which is thought to be formed from an inter-cage reaction of cage-exited O(^1D) atom with water dimer in a different cage. A hydrogen peroxide formation yield in a neon matrix is estimated to be almost unity, whereas those in argon and krypton exceed unity because of the inter-cage reaction. We concluded that neon is most appropriate media for studying the photochemistry of ozone-water complex. Wavelength dependence was studied in the solid neon. The 254- and 313-nm irradiations gave the similar results at the 355 nm irradiation, but the 365- and 633-nm irradiation did not induce any photochemical reaction. We will discuss the photochemical mechanism (dependence of wavelength and matrix cage) and the implication of the atmospheric ozone chemistry.