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Influence of the C + H2O → H2CO solid-state reaction on astrochemical networks and the formation of complex organic molecules
Astronomy & Astrophysics ( IF 5.4 ) Pub Date : 2024-12-17 , DOI: 10.1051/0004-6361/202450958 Alexey Potapov, Robin T. Garrod
Astronomy & Astrophysics ( IF 5.4 ) Pub Date : 2024-12-17 , DOI: 10.1051/0004-6361/202450958 Alexey Potapov, Robin T. Garrod
Context. The solid-state reaction C + H2O → H2CO has recently been studied experimentally and claimed as a new ‘non-energetic’ pathway to complex organic and prebiotic molecules in cold astrophysical environments.Aims. We compared results of astrochemical network modelling with and without the C + H2O surface reaction.Methods. A typical, generic collapse model in which a dense core forms from initially diffuse conditions was used along with the astrochemical kinetics model MAGICKAL.Results. The inclusion of the reaction does not notably enhance the abundance of formaldehyde itself; however, it significantly enhances the abundance of methanol (formed by the hydrogenation of formaldehyde) on the dust grains at early times, when the high gas-phase abundance of atomic C leads to relatively rapid adsorption onto the grain surfaces. As a result, the gas-phase abundance of methanol is also increased due to chemical desorption, quickly reaching abundances close to ∼10−9 nH, which decline strongly under late-time, high-density conditions. The reaction also influences the abundances of simple ice species, with the CO2 abundance increased in the earliest, deepest ice layers, while the water-ice abundance is somewhat depressed. The abundances of various complex organic molecules are also affected, with some species becoming more abundant and others less. When gas-phase atomic carbon becomes depleted, the grain-surface chemistry returns to behaviour that would be expected if there had been no new reaction.Conclusions. Our results show that fundamental reactions involving the simplest atomic and molecular species can be of great importance for the evolution of astrochemical reaction networks, thus providing motivation for future experimental and theoretical studies.
中文翻译：
C + H2O → H2CO 固相反应对天体化学网络和复杂有机分子形成的影响
上下文。H2CO →固态反应 C + H2O 最近进行了实验研究，并声称它是在寒冷的天体物理环境中获得复杂有机和益生元分子的新型“非能量”途径。目标。我们比较了有和没有 C + H2O 表面反应的天体化学网络建模的结果。方法。一个典型的通用坍缩模型，其中从最初的扩散条件中形成致密的核心，与天体化学动力学模型 MAGICKAL 一起使用。结果。该反应的加入并没有显着提高甲醛本身的丰度;然而，当原子 C 的高气相丰度导致相对较快地吸附到颗粒表面时，它显着提高了粉尘颗粒上甲醇（由甲醛氢化形成）的丰度。因此，由于化学解吸，甲醇的气相丰度也增加，迅速达到接近 ∼10-9 nH 的丰度，在后期高密度条件下丰度急剧下降。该反应还影响了简单冰种类的丰度，CO2 丰度在最早、最深的冰层中增加，而水冰丰度则略有降低。各种复杂有机分子的丰度也受到影响，一些物种变得更丰富，而另一些物种则更少。当气相原子碳耗尽时，晶粒表面的化学性质会恢复到没有新反应时所预期的行为。结论。我们的结果表明，涉及最简单的原子和分子种类的基本反应对于天体化学反应网络的演化非常重要，从而为未来的实验和理论研究提供动力。
更新日期：2024-12-18
中文翻译：
C + H2O → H2CO 固相反应对天体化学网络和复杂有机分子形成的影响
上下文。H2CO →固态反应 C + H2O 最近进行了实验研究，并声称它是在寒冷的天体物理环境中获得复杂有机和益生元分子的新型“非能量”途径。目标。我们比较了有和没有 C + H2O 表面反应的天体化学网络建模的结果。方法。一个典型的通用坍缩模型，其中从最初的扩散条件中形成致密的核心，与天体化学动力学模型 MAGICKAL 一起使用。结果。该反应的加入并没有显着提高甲醛本身的丰度;然而，当原子 C 的高气相丰度导致相对较快地吸附到颗粒表面时，它显着提高了粉尘颗粒上甲醇（由甲醛氢化形成）的丰度。因此，由于化学解吸，甲醇的气相丰度也增加，迅速达到接近 ∼10-9 nH 的丰度，在后期高密度条件下丰度急剧下降。该反应还影响了简单冰种类的丰度，CO2 丰度在最早、最深的冰层中增加，而水冰丰度则略有降低。各种复杂有机分子的丰度也受到影响，一些物种变得更丰富，而另一些物种则更少。当气相原子碳耗尽时，晶粒表面的化学性质会恢复到没有新反应时所预期的行为。结论。我们的结果表明，涉及最简单的原子和分子种类的基本反应对于天体化学反应网络的演化非常重要，从而为未来的实验和理论研究提供动力。
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