The surface reactivity of acrylonitrile with oxygen atoms on an analogue of interstellar dust grains
The surface reactivity of acrylonitrile with oxygen atoms on an analogue of interstellar dust grains
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丙烯腈与氧原子在星际尘埃颗粒类似物上的表面反应性
DOI：
10.1093/mnras/sty587
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发表时间：
2018
影响因子：
4.8
通讯作者：
Kimber H
中科院分区：
文献类型：
--
作者：
Kimber H
为揭示星际尘埃颗粒表面的低温反应性而设计的实验被用来探索氧原子与丙烯腈(C2H3CN，H2C=CH-CN)之间的非均相反应。在14K至100K的一系列固定表面温度下研究了该反应。在将反应物加到表面后，程序升温脱附与飞行时间质谱仪相结合，揭示了分子式为C3H3NO的产物的形成。这种产物是在丙烯腈反应物中添加一个氧原子的结果。氧原子的攻击似乎只发生在C=C双键，而不是涉及氰基(-CN)。氰基位置上没有反应性暗示着有机分子在尘埃颗粒上的完全饱和并不总是发生在星际介质中。模拟实验数据提供了朗缪尔-辛舍伍德式(扩散)反应机制的反应概率为0.007±0.003。从动力学模型中还求出了多层混合冰中丙烯腈、氧原子和分子氧的脱附能，分别为22.7kJ·−-1(2730K±1120K)、14.2%±110kJ·−-1(1710K±11120K)和8.5%±100.81kJ·−-1(1020K±11100K)。我们从实验中提取的动力学参数表明，原子氧和丙烯腈之间的反应可以在天体物理时间尺度上发生在星际尘埃颗粒上。
Experiments designed to reveal the low-temperature reactivity on the surfaces of interstellar dust grains are used to probe the heterogeneous reaction between oxygen atoms and acrylonitrile (C2H3CN, H2C=CH-CN). The reaction is studied at a series of fixed surface temperatures between 14 and 100 K. After dosing the reactants on to the surface, temperature-programmed desorption, coupled with time-of-flight mass spectrometry, reveals the formation of a product with the molecular formula C3H3NO. This product results from the addition of a single oxygen atom to the acrylonitrile reactant. The oxygen atom attack appears to occur exclusively at the C=C double bond, rather than involving the cyano(-CN) group. The absence of reactivity at the cyano site hints that full saturation of organic molecules on dust grains may not always occur in the interstellar medium. Modelling the experimental data provides a reaction probability of 0.007 ± 0.003 for a Langmuir–Hinshelwood style (diffusive) reaction mechanism. Desorption energies for acrylonitrile, oxygen atoms, and molecular oxygen, from the multilayer mixed ice their deposition forms, are also extracted from the kinetic model and are 22.7 ± 1.0 kJ mol−1(2730 ± 120 K), 14.2 ± 1.0 kJ mol−1(1710 ± 120 K), and 8.5 ± 0.8 kJ mol−1(1020 ± 100 K), respectively. The kinetic parameters we extract from our experiments indicate that the reaction between atomic oxygen and acrylonitrile could occur on interstellar dust grains on an astrophysical time-scale.