At low temperatures (∼10 K), hydrogen atoms can diffuse quickly on grain ice mantles and frequently encounter hydrogen molecules, which cover a notable fraction of grain surface. The desorption energy of H atoms on H₂ substrates is much less than that on water ice. The H atom encounter desorption mechanism is adopted to study the enhanced desorption of H atoms on H₂ substrates. Using a small reaction network, we show that the steady-state surface H abundances predicted by the rate equation model that includes H atom encounter desorption agree reasonably well with the results from the more rigorous microscopic Monte Carlo method. For a full gas-grain model, H atom encounter desorption can reduce surface H abundances. Therefore, if a model adopts the encounter desorption of H atoms, it becomes more difficult for hydrogenation products such as methanol to form, but it is easier for C, O and N atoms to bond with each other on grain surfaces.

在低温（~10 K）下，氢原子可以在颗粒冰幔上快速扩散并经常遇到氢分子，氢分子覆盖了颗粒表面的显着部分。H ₂底物上H原子的解吸能远小于水冰上的解吸能。采用H原子遇到解吸机理研究H原子对H ₂的增强解吸基材。使用小型反应网络，我们表明，包括 H 原子遇到解吸的速率方程模型预测的稳态表面 H 丰度与更严格的微观蒙特卡罗方法的结果相当吻合。对于完整的气粒模型，H 原子遇到解吸会降低表面 H 丰度。因此，如果模型采用H原子的遭遇解吸，则甲醇等加氢产物更难形成，但C、O和N原子更容易在晶粒表面相互键合。