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Halogen Radical Chemistry at Aqueous Interfaces

机译:水界面的卤素自由基化学

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Halogens play key roles in the chemical composition of marine boundary layers, the free troposphere and the stratosphere. Atmospheric halogen chemistry is dominated by reactions between gas-phase and aqueous species on the surfaces of the ocean and marine aerosol. The mechanisms of interfacial halogen radical/halide reactions, however, are not fully understood, partly due to the dearth of techniques for in situ monitoring of the products and intermediates of fast interfacial halogen radical reactions. Here, we report the online electrospray mass spectrometric identification of the species produced on the surface of aqueous Br- and I- microjets collided by I-center dot(g) pulses generated from the 266 nm laser photolysis of CH3I/O-2/N-2 gas mixtures. Mass-specific identification of intermediates and products in D2O and (H2O)-O-18 solutions and their dependences on I-center dot(g) fluxes let us outline mechanisms of formation. We found that the uptake of I-center dot(g) on the surface of Br- and I- microjets (effective uptake coefficient gamma(eff) >= 2 x 10(-4)) yields IBr center dot-/I-2(center dot-) radical intermediates, which rapidly react with additional I-center dot to produce trihalides I2Br-/IBr2-/I-3(-) plus I3On- (n = 1, 2) species within similar to 10 its. Our findings point to a new halogen activation pathway initiated by photogenerated I-center dot.
机译:卤素在海洋边界层,自由对流层和平流层的化学组成中起着关键作用。大气卤素化学物质主要由海洋和海洋气溶胶表面上的气相和水性物质之间的反应引起。但是,界面卤代自由基/卤化物反应的机理尚未得到充分理解,部分原因是缺乏用于现场监测快速界面卤代自由基反应的产物和中间体的技术的缺乏。在这里,我们报告了在线电喷雾质谱鉴定的水和Br-和I-微喷的表面上产生的物质,该物质被CH3I / O-2 / N的266 nm激光光解产生的I-中心点(g)脉冲碰撞-2混合气体。 D2O和(H2O)-O-18溶液中的中间体和产物的质量特异性鉴定及其对I-中心dot(g)助焊剂的依赖性,让我们概述了形成机理。我们发现在Br-和I-微喷头表面吸收I-中心点(g)(有效吸收系数gamma(eff)> = 2 x 10(-4))产生IBr中心点-/ I-2 (中心点)自由基中间体,它们与其他I-中心点快速反应,生成三卤化物I2Br- / IBr2- / I-3(-)加上I3On-(n = 1,2)物种,其相似度约为10。我们的发现指出了由光生I中心点引发的新的卤素活化途径。

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