Cazaux Stéphanie, Boschman Leon, Rougeau Nathalie, Reitsma Geert, Hoekstra Ronnie, Teillet-Billy Dominique, Morisset Sabine, Spaans Marco, Schlathölter Thomas
Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, NL 9700 AV Groningen, The Netherlands.
Leiden Observatory, Leiden University, P.O. Box 9513, NL 2300 RA Leiden, The Netherlands.
Sci Rep. 2016 Jan 29;6:19835. doi: 10.1038/srep19835.
The understanding of hydrogen attachment to carbonaceous surfaces is essential to a wide variety of research fields and technologies such as hydrogen storage for transportation, precise localization of hydrogen in electronic devices and the formation of cosmic H2. For coronene cations as prototypical Polycyclic Aromatic Hydrocarbon (PAH) molecules, the existence of magic numbers upon hydrogenation was uncovered experimentally. Quantum chemistry calculations show that hydrogenation follows a site-specific sequence leading to the appearance of cations having 5, 11, or 17 hydrogen atoms attached, exactly the magic numbers found in the experiments. For these closed-shell cations, further hydrogenation requires appreciable structural changes associated with a high transition barrier. Controlling specific hydrogenation pathways would provide the possibility to tune the location of hydrogen attachment and the stability of the system. The sequence to hydrogenate PAHs, leading to PAHs with magic numbers of H atoms attached, provides clues to understand that carbon in space is mostly aromatic and partially aliphatic in PAHs. PAH hydrogenation is fundamental to assess the contribution of PAHs to the formation of cosmic H2.
理解氢与碳质表面的附着对于广泛的研究领域和技术至关重要，例如用于交通运输的氢存储、电子设备中氢的精确定位以及宇宙中H₂的形成。对于作为典型多环芳烃（PAH）分子的蔻阳离子，氢化过程中幻数的存在已通过实验揭示。量子化学计算表明，氢化遵循特定的位点顺序，导致出现附着有5、11或17个氢原子的阳离子，这与实验中发现的幻数完全一致。对于这些闭壳阳离子，进一步氢化需要与高过渡势垒相关的明显结构变化。控制特定的氢化途径将提供调整氢附着位置和系统稳定性的可能性。导致附着有氢原子幻数的PAH氢化序列，为理解太空中的碳在PAH中大多为芳香性且部分为脂肪族提供了线索。PAH氢化对于评估PAH对宇宙H₂形成的贡献至关重要。
