Surface reactions of atoms and the mechanism of deuterium fractionation on inter Stellar dusts at the very low temperature

这项计划的目的是获得通过原子表面反应形成星际分子的反应通道和速率，并揭示所观察到的甲醇分子中氢的富集源。我们的研究结果概括如下：1.在固体CO分子中，氘原子的加成速度仅为氢加成反应的十分之一，这表明在甲醇的第一步中，氢原子的加成反应不太可能进行。2.我们证实了在~10K下，CH_3OH-d_n(CH_3OH-d_n D→CH_3OH-d_&lt；n 1&gt；n=0-2)中的H-D取代反应在固相中进行。取代反应速率随甲醇中D原子个数n的增加而减小。我们首次证明了所观察到的重氢的部分富集化可以通过颗粒-表面反应实现。我们的定量数据表明，在分子云中，H-D取代比分子云中连续的重氢与CO的加成反应更有效地生成重氢甲醇。

This project was carried out for the purpose of obtaining the reaction channels and rates of the formation of interstellar molecules via surface reactions of atoms and also revealing the origin of deuterium enrichment in methanol molecules observed. We summarize the results of our research as follows.1.The rate of addition of deuterium atoms to solid CO molecule is as slow as one-tenths of that of hydrogen addition, indicating that the deuterium addition is unlikely for the first step of the deuterium enrichment of methanol.2.We confirmed that H-D substitution reactions in CH_3OH-d_n(CH_3OH-d_n+D→CH_3OH-d_<n+1>,n=0-2) proceed in solid phase at 〜10K. The reaction rates of the substitution decrease as number of D atoms in methanol, n, increases3.We demonstrated for the first time that deuterium enrichment observed can be achieved partly by the grain-surface reactions. Our quantitative data shows that H-D substitution is more efficient to produce deuterated methanol than the successive deuterium addition to CO in a molecular cloud.