Rate of H2 formation on amorphous grains
Rate of H2 formation on amorphous grains
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无定形颗粒上的 H2 形成速率
DOI：
10.1007/bf00648648
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发表时间：
1981
影响因子：
1.9
通讯作者：
R. Smoluchowski
中科院分区：
文献类型：
--
作者：
R. Smoluchowski
假设晶粒是单晶、多晶或非晶态，则分析晶粒上吸附的氢原子形成分子氢的速率。在多晶晶粒和石墨片上，该速率可能比单晶粒低几个数量级。对于非晶晶粒来说也是如此，因为在低温下，只有吸收在相邻位点上的原子才能形成分子。推导出合适的公式并与单晶粒的经典结果进行比较。给出了结晶冰和非晶冰的定量结果，但只要稍加改变，这些结果也应该适用于其他固体。如果 H 原子的密度高且 H2 分子的密度低，并且只有当晶粒的温度满足冰和石墨导致接近 15-17 K 的值的关系时，非晶晶粒的速率可以接近晶粒的速率，在 10 倍左右的范围内。这个最大速率仅比晶粒完全被 H2 层覆盖且反应停止时的温度高出约一个度。此外，对于恒定的晶粒数密度，非晶晶粒上的速率是二阶的，而晶粒上的速率是一阶的。这两种情况都预测无定形颗粒会导致具有不规则且轮廓清晰的特征的氢云，这与晶粒上形成的更均匀的云形成鲜明对比。
The rate of formation of molecular hydrogen from hydrogen atoms adsorbed on grains is analyzed, assuming that the grains are single crystals, polycrystalline or amorphous. On polycrystalline grains, and on graphite platelets, this rate could be orders of magnitude lower than on single crystal grains. The same is true for amorphous grains because there, at low temperatures, only atoms absorbed on neighboring sites can form molecules. Suitable formulae are derived and compared with the classical results for single crystal grains. Quantitative results are given for crystalline and amorphous ice, but with small changes these should also be valid for other solids. The rates for amorphous grains can approximate, within a factor of 10 or so, those for crystalline grains if the density of H atoms is high and the density of H2molecules is low and only when the temperature of the grains satisfies a relation which for ice and graphite leads to a value in the proximity of 15–17 K. This maximum rate occurs only a degree or so above the temperature at which the grains are totally covered by an H2layer and the reaction ceases. Furthermore, for a constant number density of grains, the rates on amorphous grains are second order while those on crystalline grains are first order. Both these circumstances predict amorphous grains to lead to H2clouds with irregular and sharply delineated features in contrast to more uniform clouds formed on crystalline grains.