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arXiv 1209.2540astro-ph.GAastro-ph.SR
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颗粒表面c-C2H4O形成的模拟

Modelling of c-C2H4O formation on grain surfaces

A. Occhiogrosso, S. Viti, M. D. Ward, S. D. Price

摘要:

尽管环氧乙烷(c-C2 H4 O)由于环张力而具有潜在的反应性,但它是一种复杂的分子,在星际致密核心的物理条件下似乎是稳定的;事实上,它已经在几个高质量恒星形成区域被检测到,其柱密度为10 e13 cm-2(Ikeda et al. 2001)。到目前为止,它的观测丰度不能通过化学模型再现,这可能是由于它的化学作用对颗粒表面的重要贡献。最近,Ward和Price(2011)进行了实验,以研究从氧原子和乙烯冰作为反应物开始的环氧乙烷的表面形成。我们提出了一个化学模型,其中包括Ward和Price(2011)关于c-C2 H4 O形成的最新实验结果。我们研究了致密核的物理参数对c-C2 H4 O丰度的影响。我们证实,环氧乙烷确实可以形成在冷阶段(当ISM致密的核心形成),通过添加一个氧原子在整个乙烯分子的C=C双键,并释放热解吸在热核心阶段。我们的理论结果和观测结果之间的定性比较表明,我们能够重现对高质量的恒星形成区域的环氧乙烷的丰度。

英文摘要:

Despite its potential reactivity due to ring strain, ethylene oxide (c-C2H4O) is a complex molecule that seems to be stable under the physical conditions of an interstellar dense core; indeed it has been detected towards several high-mass star forming regions with a column density of the order of 10e13cm-2 (Ikeda et al. 2001). To date, its observational abundances cannot be reproduced by chemical models and this may be due to the significant contribution played by its chemistry on grain surfaces. Recently, Ward and Price (2011) have performed experiments in order to investigate the surface formation of ethylene oxide starting with oxygen atoms and ethylene ice as reactants. We present a chemical model which includes the most recent experimental results from Ward and Price (2011) on the formation of c-C2H4O. We study the influence of the physical parameters of dense cores on the abundances of c-C2H4O. We verify that ethylene oxide can indeed be formed during the cold phase (when the ISM dense cores are formed), via addition of an oxygen atom across the C=C double bond of the ethylene molecule, and released by thermal desorption during the hot core phase. A qualitative comparison between our theoretical results and those from the observations shows that we are able to reproduce the abundances of ethylene oxide towards high-mass star-forming regions.

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