Mechanism of Atomic Hydrogen Addition Reactions on np-ASW
Mechanism of Atomic Hydrogen Addition Reactions on np-ASW
复制标题
np-ASW 上的原子氢加成反应机理
DOI：
10.3847/1538-4357/aa9a3e
复制
发表时间：
2017
期刊：
影响因子：
--
通讯作者：
G. Vidali
中科院分区：
文献类型：
--
作者：
Jiao He;Shahnewaj M. Emtiaz;G. Vidali
氢是最丰富的元素，是星际尘埃颗粒上发生的许多（如果不是大多数）反应的驱动力。在氢原子加成反应中，速率通常由氢原子而不是其他反应伙伴的表面动力学决定。存在三种机制可以解释表面上的氢加成反应：Langmuir-Hinshelwood、Eley-Rideal 和热原子。在气体颗粒模型中，假设的机制极大地影响模拟结果。在这项工作中，我们通过研究 H+O3 O2+OH 在无孔无定形固体水 (np-ASW) 薄膜表面上在 10 至 50 K 的温度范围内的反应，量化了原子氢加成反应速率的温度依赖性。发现反应速率与温度无关。这与速率方程网络的模拟结果不一致，速率方程网络假设通过热扩散或隧道扩散实现 Langmuir-Hinshelwood 机制；假设这种机制的反应速率具有强烈的温度依赖性，无论是明确的还是隐含的，这是实验上没有发现的。我们认为 Eley-Rideal 和/或热原子机制在氢原子加成反应中发挥着关键作用，并且应该包含在气体颗粒模型中。我们还建议我们新开发的时间分辨反应散射可用于测量颗粒表面反应中的化学解吸效率。
Hydrogen, being the most abundant element, is the driver of many if not most reactions occurring on interstellar dust grains. In hydrogen atom addition reactions, the rate is usually determined by the surface kinetics of the hydrogen atom instead of the other reaction partner. Three mechanisms exist to explain hydrogen addition reactions on surfaces: Langmuir–Hinshelwood, Eley–Rideal, and hot-atom. In gas-grain models, the mechanism that is assumed greatly affects the simulation results. In this work, we quantify the temperature dependence of the rates of atomic hydrogen addition reactions by studying the reaction of H+O3 O2+OH on the surface of a film of non-porous amorphous solid water (np-ASW) in the temperature range from 10 to 50 K. The reaction rate is found to be temperature independent. This disagrees with the results of simulations with a network of rate equations that assume Langmuir–Hinshelwood mechanism through either thermal diffusion or tunneling diffusion; the reaction rates assuming such a mechanism possesses a strong temperature dependence, either explicitly or implicitly, that is not seen experimentally. We suggest that the Eley–Rideal and/or hot-atom mechanism play a key role in hydrogen atom addition reactions, and should be included in gas-grain models. We also suggest that our newly developed time-resolved reactive scattering can be utilized to measure the chemical desorption efficiency in grain surface reactions.
DOI：
--
发表时间：
2011
期刊：
影响因子：
--
作者：
Masahiro Nakashima;他;Y.Niimi;T. Hama
通讯作者：
T. Hama