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首页> 外文期刊>The Astrophysical journal >ACTIVATION ENERGY OF C-H BOND FORMATION IN CARBON GRAINS IRRADIATED WITH HYDROGEN ATOMS
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ACTIVATION ENERGY OF C-H BOND FORMATION IN CARBON GRAINS IRRADIATED WITH HYDROGEN ATOMS

机译：氢原子辐照碳粒中C-H键形成的活化能

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摘要

We present the results of an experimental study of the interaction of nano-sized hydrogen-free carbon grains with H atoms of different temperatures. The effects of H irradiation have been analyzed in situ with infrared spectroscopy. Exposure of carbon grains to atomic hydrogen results in the formation of aliphatic C-H bonds. The formation cross section has been derived from the increase of the intensity of the C-H stretching band with H atom fluence. The cross section decreases with decreasing H beam temperature. We have estimated an activation energy of aliphatic C-H bonds of 6 meV (～70 K), a value considerably lower than the barrier for chemisorption of H atoms on graphite. This result suggests that in dense clouds hydrogenation of carbon grains by atomic hydrogen cannot counteract destruction of C-H bonds by cosmic rays and internal UV field, even if ice mantles are absent. The small activation energy, obtained on realistic analogs of interstellar carbon dust, supports theoretical models that predict an important role of chemisorption on carbon grains in the formation of H_2.
机译：我们提出了纳米级无氢碳晶粒与不同温度的H原子相互作用的实验研究结果。 H辐射的影响已经用红外光谱原位分析。碳粒暴露于原子氢导致形成脂肪族C-H键。形成截面是由随着H原子通量增加C-H拉伸带的强度而得出的。横截面随着H射线温度的降低而减小。我们估计脂肪族C-H键的活化能为6 meV（〜70 K），该值大大低于H原子在石墨上化学吸附的能级。该结果表明，在密云中，即使不存在冰幔，原子氢对碳晶粒的氢化也不能抵消宇宙射线和内部紫外线场对C-H键的破坏。从星际碳尘的真实类似物获得的小活化能支持理论模型，这些模型预测了化学吸附对碳粒在H_2形成中的重要作用。

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