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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Direct Measurement of Surface Residence Times: Nitryl Chloride and Chlorine Nitrate on Alkali Halides at Room Temperature
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Direct Measurement of Surface Residence Times: Nitryl Chloride and Chlorine Nitrate on Alkali Halides at Room Temperature

机译：表面停留时间的直接测量：室温下在碱性卤化物上的氯化氯化镍和硝酸氯

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摘要

To gain quantitative understanding of the "stickiness" of a molecule on a given surface, we have developed a new diffusion tube method that allows us to measure changes in the surface residence times of unreactive as well as reactive adsorbants on solid substrates in real time. The experiment involves sending a pulse of molecules through a tube coated internally with a material of interest. The arrival time of the pulse is recorded using a mass spectrometer, which is mounted at the tube exit in a high vacuum chamber. Since the number of wall collisions under molecular flow conditions is determined only by the tube geometry, the surface residence time can be calculated on a per collision basis. A Monte Carlo simulation, based on the assumption that the molecules are reflected upon collision with a cosine directional distribution, is used to model experimental results. In this study we have measured the surface residence times of two reactive, atmospherically relevant molecules, ClNO_2 and ClONO_2, on sea-salt aerosol mimics (NaCl, KBr). We found an upper limit of 0.02 ms for the interaction of ClNO_2 with KBr and a surface residence time of 0.7 ± 0.2 ms for ClONO_2 on NaCl at uptake coefficients of γ = 0.0002 and 0.1, respectively.
机译：为了定量了解给定表面上的分子的“粘性”，我们开发了一种新的扩散管方法，该方法可以实时测量固体基质上未反应和反应性吸附剂的表面停留时间的变化。实验涉及通过内部涂覆有目标材料的管子发送分子脉冲。使用质谱仪记录脉冲的到达时间，该质谱仪安装在高真空室内的管出口处。由于分子流动条件下壁碰撞的次数仅由管的几何形状决定，因此可以基于每个碰撞来计算表面停留时间。基于假设分子在碰撞时具有余弦方向分布的情况下进行反射的蒙特卡洛模拟用于对实验结果进行建模。在这项研究中，我们测量了两个与大气相关的反应性分子ClNO_2和ClONO_2在海盐气溶胶模拟物（NaCl，KBr）上的表面停留时间。我们发现ClNO_2与KBr相互作用的上限为0.02 ms，ClONO_2在NaCl上的吸收系数分别为γ= 0.0002和0.1时，表面停留时间为0.7±0.2 ms。

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