The "non-reaction" of ground-state triplet carbon atoms with water revisited.
The "non-reaction" of ground-state triplet carbon atoms with water revisited.
复制标题
DOI：
10.1002/cphc.200500555
复制
发表时间：
2006-04
期刊：
影响因子：
--
通讯作者：
Peter R. Schreiner;H. Reisenauer
中科院分区：
文献类型：
--
作者：
Peter R. Schreiner;H. Reisenauer
我们介绍了一种新的实验装置产生的碳原子的脉冲激光烧蚀的脉冲速率优化，以避免变暖的矩阵。这种技术与基质退火、再冷却和光谱记录（例如IR）的结合使我们能够区分在基质隔离条件下三重态和单重态碳原子对水的反应性。我们的实验程序确保所有未反应的碳原子的弛豫到其三重基态在10 K矩阵光谱记录之前。与CCSD（T）/cc-pVTZ+ZPVE计算数据和早期较低水平的结果一致，我们发现三重态碳原子确实不与水反应，尽管它们的初始能量很高。三重态到单重态的羟基卡宾的系统间交叉不太重要，因为三重态碳原子和水的初始复合物重排为共价结合的物质的势垒太高，并且更可能解离。我们没有发现三重态碳原子直接插入O-H键的证据。三重态碳原子的自缩合反应显然是有利的，并产生显示其自身反应性的碳簇。因此，在外星环境中形成的醛糖只能来自“热”碳原子或通过光反应。
We introduce a novel experimental setup for the generation of carbon atoms by means of pulsed laser ablation with a pulse rate optimized to avoid warming of the matrix. The combination of this technique with annealing of the matrix, recooling, and spectral recording (e.g. IR) allowed us to differentiate between the reactivity of triplet and singlet carbon atoms towards water under matrix-isolation conditions. Our experimental procedure assures the relaxation of all unreacted carbon atoms to their triplet ground state in the 10 K matrix before spectral recording. In agreement with CCSD(T)/cc-pVTZ+ZPVE computational data and earlier lower level results, we find that triplet carbon atoms indeed do not react with water, despite their high initial energy. Intersystem crossing of the triplet to singlet states of hydroxy carbene are less important, as the barriers for rearrangement of the initial complex of triplet carbon atoms and water to covalently bound species are too high, and dissociation is more likely. We found no evidence for a direct O--H bond-insertion path for triplet carbon atoms. Self-condensation reactions of triplet carbon atoms are clearly favored and yield carbon clusters that show reactivity of their own. The proposed formation of aldoses in extraterrestrial environments can therefore only derive from "hot" carbon atoms or through photoreactions.