Laboratory surface and solid state astrochemistry of biomolecular precursors on grain mimics
Laboratory surface and solid state astrochemistry of biomolecular precursors on grain mimics
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颗粒模拟物上生物分子前体的实验室表面和固态天体化学
DOI：
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发表时间：
2013
期刊：
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通讯作者：
A. G. M. Abdulgalil
中科院分区：
文献类型：
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作者：
A. G. M. Abdulgalil
水（H2O）和乙腈（CH3CN）在各种地外环境中的存在引起了相当大的关注，因为这两种分子对了解生命的起源至关重要。本文采用超高真空表面科学方法（反射-吸收红外光谱、温度程序解吸、质子和电子辐照实验）研究了CH3CN和H2O冰在非晶二氧化硅表面的物理和化学相互作用，以了解这些分子在空间环境中受到辐射和热处理时的行为。CH3CN在H2O和二氧化硅表面上的热行为是由分子间力的平衡控制的，并显示出二氧化硅表面的润湿（在多层生长之前形成明显的第一吸附层）和水表面的脱湿或岛状形成（所有CH3CN暴露的多层生长）的证据。这说明了衬底在确定固态生长形态中的重要性。研究了250 ~ 500 eV电子在CH3CN和H2O体系中诱导的物理和化学过程。这种相互作用只促进CH3CN和H2O冰表面的解吸。相比之下，意大利合作者进行的200 keV质子辐照CH3CN冰的实验显示，固体CH3CN中存在化学反应的证据。解吸和反应截面的定量测量被用来调和这种鲜明的对比。这些与水有关的过程对天体物理学的影响是通过简单的数值模拟来研究的。
The existence of water (H2O) and acetonitrile (CH3CN) in various extraterrestrial environments attracts considerable attention as both molecules are crucial to understanding the genesis of life. This thesis involves investigations of the physical and chemical interactions of CH3CN and H2O ices condensed on an amorphous silica surface using ultrahigh vacuum-based surface science methods (reflection-absorption infrared spectroscopy, temperature programmed desorption, protonand electronirradiation experiments) in an effort to understand how such molecules will behave when they are processed by radiation and heat in space environments. The thermal behaviour of CH3CN on H2O and on the silica surface is governed by a balance of intermolecular forces and shows evidence for wetting of the silica surface (formation of a distinct first adsorption layer before multilayer growth) and of dewetting or island formation on the H2O surface (multilayer growth for all CH3CN exposures). This illustrates the importance of the substrate in determining the solid state growth morphology. Physical and chemical processes induced by 250 to 500 eV electrons have been investigated in the CH3CN and H2O systems. Such interactions promote only desorption from both CH3CN and H2O ice surfaces. 200 keV protons irradiation experiments of CH3CN ices, conducted by collaborators in Italy, in contrast showed evidence for chemical reactions in the solid CH3CN. Quantitative measurements of desorption and reaction cross-sections are used to reconcile this stark contrast. The impact of such processes in relation to H2O on astrophysics is investigated through simple numerical simulations using results derived from this work.