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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Sensitivity studies of methane photolysis and its impact on hydrocarbon chemistry in the atmosphere of Titan
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Sensitivity studies of methane photolysis and its impact on hydrocarbon chemistry in the atmosphere of Titan

机译：泰坦大气中甲烷光解的敏感性研究及其对烃化学的影响

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The photodissociation of methane at Lyman alpha (1216 Angstrom) has been the focus of much scrutiny over the past few years. Methane photolysis leads to the formation of H-2 molecules as well as H, CH, (CH2)-C-1, (CH2)-C-3, and CH3 radicals, which promote the propagation of hydrocarbon chemistry. However, recent studies [Mordaunt et al., 1993; Romani, 1996; Smith and Raulin, 1999] have not fully resolved the issue of methane photolytic product yields at this wavelength. We use a one-dimensional photochemical model with updated chemistry to investigate the significance of these quantum yield schemes on the hydrocarbon chemistry of Titan's atmosphere, where Lyman a radiation accounts for 75% of methane photolysis longward of 1000 Angstrom. Sensitivity studies show that while simple hydrocarbons like C2H2 (acetylene) and C2H4 (ethylene), which serve as important intermediates to the formation of more complex hydrocarbons, show virtually no variation in abundance, minor C-3 molecules do show substantial sensitivity to choice of quantum yield scheme. We find that the C3H4 isomers (methylacetylene, allene) and C3H6 (propylene) display major variation in atmospheric mixing ratios under the implementation of these schemes, with a maximum variation of approximately a factor of 5 in C3H4 abundance and approximately a factor of 4 for C3H6. In these cases our nominal scheme, recommended by Romani [1996], offers an intermediate result in comparison with the other schemes. We also find that choice of pathway for non-Lyman alpha methane absorption does affect hydrocarbon chemistry in the atmosphere of Titan, but this effect is minimal. A 65% variation in C2H6 (ethane) abundance, a value within observational uncertainty, is the largest divergence found for a wide range of possible non-Lyman alpha photofragment quantum yields. These results will have significance in future modeling and interpretation of observations of the atmosphere of Titan. [References: 52]
机译：在过去的几年中，甲烷在Lymanα（1216埃）处的光解离一直是许多研究的重点。甲烷的光解导致形成H-2分子以及H，CH，（CH2）-C-1，（CH2）-C-3和CH3自由基，从而促进了烃化学的传播。但是，最近的研究[Mordaunt等，1993; M。罗曼尼（Romani），1996年; Smith和Raulin，1999年]尚未完全解决在该波长下甲烷光解产物收率的问题。我们使用一维光化学模型和更新的化学方法来研究这些量子产率方案对泰坦大气中碳氢化合物化学的重要性，其中，Lyman辐射占甲烷光解作用的75％，直到1000埃为止。敏感性研究表明，虽然作为C2H2（乙炔）和C2H4（乙烯）的重要烃类（是形成更复杂烃类的重要中间体）的简单烃类实际上在丰度上没有变化，但次要C-3分子的确对选择C3H3分子表现出相当大的敏感性。量子产率方案。我们发现，在这些方案的实施下，C3H4异构体（甲基乙炔，丙二烯）和C3H6（丙烯）显示出大气混合比的主要变化，C3H4丰度的最大变化约为5，而C3H4丰度的最大变化约为4。 C3H6。在这些情况下，由Romani [1996]推荐的名义方案与其他方案相比提供了中间结果。我们还发现非莱曼α甲烷吸收途径的选择确实会影响泰坦大气中的碳氢化合物化学，但​​是这种影响很小。 C2H6（乙烷）丰度的65％变化是观测不确定性内的一个值，是对大范围可能的非莱曼α光片段量子产率的最大发现。这些结果将对未来的泰坦大气观测建模和解释具有重要意义。 [参考：52]

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