论文标题
气体化学模型对表面反应障碍的敏感性：关键碳插入反应的影响，C + H $ _2 $ $ \ rightarrow $ ch $ _2 $
Sensitivity of gas-grain chemical models to surface reaction barriers: Effect from a key carbon-insertion reaction, C + H$_2$ $\rightarrow$ CH$_2$
论文作者
论文摘要
当代气体元素模型的可行性取决于精确的动力学数据的可用性，尤其是在表面过程中。我们研究了气体化学模型对某些最丰富物种之间重要表面反应的能量屏障EA的敏感性：C和H2（表面C +表面H2 =表面CH2）。我们使用气体粒度炼金术对时间相关的化学演化进行建模（nh：10^{3} -10^{12} {12} cm^{ - 3}）和温度（t：10-300 k），假定UV-dark（av = 20 mag）和部分uv-irrAdied（avel）的情况（AV-irratied at Magrand）是典型的典范。我们考虑了表面反应的能屏障的两个值，EA = 2500 K（最初在网络中实现）和EA = 0 K（如实验室中测量并通过量子化学模拟计算）。我们发现，如果C + H2 = CH2表面反应是无障碍的，则会发生表面碳原子更快地转化为甲烷冰。 CHN碳氢化合物的过量生产会影响更复杂的碳氢化合物，氰化物和硝酸盐以及低温<10-15 K的含CS的物种。CO的表面氢化，因此也会影响复合物（有机）分子的合成。 As a result, important species whose abundances may change by more than a factor of two at 1 Myr include atomic carbon, small mono-carbonic (C1) and di-carbonic (C2) hydrocarbons, CO2, CN, HCN, HNC, HNCO, CS, H2CO, H2CS, CH2CO, and CH3OH (in either gas and/or ice).关键物种，CO，H2O和N2的丰度以及O，HCO+，N2H+，NH3，NO和大多数S含S含的分子几乎不受影响。表面反应屏障的进一步准确的实验室测量和量子化学计算对于提高星体化学模型的准确性至关重要。
The feasibility of contemporary gas-grain astrochemical models depends on the availability of accurate kinetics data, in particular, for surface processes. We study the sensitivity of gas-grain chemical models to the energy barrier Ea of the important surface reaction between some of the most abundant species: C and H2 (surface C + surface H2 = surface CH2). We used the gas-grain code ALCHEMIC to model the time-dependent chemical evolution over a 2D grid of densities (nH: 10^{3} - 10^{12}cm^{-3}) and temperatures (T: 10 - 300 K), assuming UV-dark (Av = 20 mag) and partly UV-irradiated (Av = 3 mag) conditions that are typical of the dense interstellar medium. We considered two values for the energy barrier of the surface reaction, Ea = 2500 K (as originally implemented in the networks) and Ea = 0 K (as measured in the laboratory and computed by quantum chemistry simulations). We find that if the C + H2 = CH2 surface reaction is barrierless, a more rapid conversion of the surface carbon atoms into methane ice occurs. Overproduction of the CHn hydrocarbon ices affects the surface formation of more complex hydrocarbons, cyanides and nitriles, and CS-bearing species at low temperatures < 10-15 K. The surface hydrogenation of CO and hence the synthesis of complex (organic) molecules become affected as well. As a result, important species whose abundances may change by more than a factor of two at 1 Myr include atomic carbon, small mono-carbonic (C1) and di-carbonic (C2) hydrocarbons, CO2, CN, HCN, HNC, HNCO, CS, H2CO, H2CS, CH2CO, and CH3OH (in either gas and/or ice). The abundances of key species, CO, H2O, and N2 as well as O, HCO+, N2H+, NH3, NO, and most of the S-bearing molecules, remain almost unaffected. Further accurate laboratory measurements and quantum chemical calculations of the surface reaction barriers will be crucial to improve the accuracy of astrochemical models.
