DNA核碱基胞嘧啶的飞秒系统间穿越
Femtosecond Intersystem Crossing in the DNA Nucleobase Cytosine
摘要：
采用从头算分子动力学方法，包括非绝热耦合和自旋轨道耦合，研究了胞嘧啶在紫外光吸收后的失活过程。系统间穿越（ISC）被发现在几十飞秒内直接与内转换竞争，从而使胞嘧啶成为迄今为止计算出的具有最快三重态人口的有机化合物。研究发现，单重态和三重态之间的密切简并可以超过补偿非常小的自旋轨道耦合，导致有效的ISC。飞秒性质的系统间穿越过程突出了其在光化学的重要性，并挑战了传统的观点，即大的单重态-三重态耦合需要一个有效的人口流入三重态。这些发现对于理解DNA的光稳定性以及有机分子的光化学和动力学具有重要意义。
英文摘要：
Ab initio molecular dynamics including non-adiabatic and spin-orbit couplings on equal footing is used to unravel the deactivation of cytosine after UV light absorption. Intersystem crossing (ISC) is found to compete directly with internal conversion in tens of femtoseconds, thus making cytosine the organic compound with the fastest triplet population calculated so far. It is found that close degeneracy between singlet and triplet states can more than compensate for very small spin-orbit couplings, leading to efficient ISC. The femtosecond nature of the intersystem crossing process highlights its importance in photochemistry and challenges the conventional view that large singlet-triplet couplings are required for an efficient population flow into triplet states. These findings are important to understand DNA photostability and the photochemistry and dynamics of organic molecules in general.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
