Intersystem crossing in the exit channel
Intersystem crossing in the exit channel
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DOI：
10.1038/s41557-018-0186-5
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发表时间：
2018-12
期刊：
影响因子：
21.8
通讯作者：
Hongwei Li;Alexander Kamasah;S. Matsika;A. Suits
中科院分区：
文献类型：
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作者：
Hongwei Li;Alexander Kamasah;S. Matsika;A. Suits
系间交叉在光化学中起着重要的作用。据了解，当由于强自旋-轨道耦合而存在重原子时，或者当形成强结合的长寿命复合物时，这是有效的，这增加了发现单重态-三重态交叉缝的机会。在这里，我们提出了一个不同的系统间交叉机制的证据在双分子反应的O（3 P）与烷基胺。在交叉束实验中，产品的速度-通量图测量从H提取从甲基产生的氨基烷基自由基，这也给OH自由基作为共同片段。产物的低能释放和各向同性角分布表明，这种反应在产生OH和氨烷基之前经历了络合物的形成。然而，在三重态势能面上没有阱可以支持这样的复合物。多参考从头计算表明，相反，系统间的交叉发生在出口通道区域，由于长距离偶极偶极相互作用的新生自由基产物对耦合消失的单线态-三线态分裂在长距离。系统间的交叉，然后导致一个深刻的羟胺之前，OH消除。
Intersystem crossing plays an important role in photochemistry. It is understood to be efficient when heavy atoms are present due to strong spin–orbit coupling, or when strongly bound long-lived complexes are formed that increase the chance of finding the singlet–triplet intersection seam. Here we present evidence for a different intersystem crossing mechanism in the bimolecular reaction of O(3P) with alkylamines. In crossed-beam experiments, product velocity–flux maps are measured for aminoalkyl radicals produced from H abstraction from the methyl group, which also gives OH radicals as co-fragments. The low translational-energy release and isotropic angular distributions of the products indicate that such reactions undergo the formation of a complex before OH and aminoalkyl are produced. However, there is no well on the triplet potential energy surface that could support such a complex. Multi-reference ab initio calculations suggest, instead, that intersystem crossing occurs in the exit-channel region due to the long-range dipole–dipole interaction between the nascent radical product pair coupled with the vanishing singlet–triplet splitting at long range. Intersystem crossing then leads to a deep hydroxylamine well before OH elimination.