Institut für Physikalische Chemie, Friedrich-Schiller-Universität Jena, Helmholtzweg 4, 07743 Jena, Germany.
Chemphyschem. 2010 Dec 3;11(17):3617-24. doi: 10.1002/cphc.201000557.
Using mixed quantum-classical dynamics, the lowest part of the UV absorption spectrum and the first deactivation steps of keto-cytosine have been investigated. The spectrum shows several strong peaks, which mainly come from the S(1) and S(2) states, with minor contributions from the S(3). The semiclassical trajectories, launched from these three states, clearly indicate that at least four states are involved in the relaxation of keto-cytosine to the ground state. Non-adiabatic transfer between the ππ* and nπ* excited states and deactivation via three-state conical intersections is observed in the very early stage of the dynamics. In less than 100 fs, a large amount of population is deactivated to the ground state via several mechanisms; some population remains trapped in the S(2) state. The latter two events can be connected to the fs and ps transients observed experimentally.
使用混合量子经典动力学，研究了酮基胞嘧啶的紫外吸收光谱的最低部分和最初的失活步骤。该光谱显示出几个强峰，主要来自 S(1)和 S(2)态，S(3)态的贡献较小。从这三个态发射的半经典轨迹清楚地表明，至少有四个态参与了酮基胞嘧啶弛豫到基态的过程。在动力学的早期阶段，观察到 ππ和 nπ激发态之间的非绝热转移以及通过三态锥形交叉失活。在不到 100 fs 的时间内，大量的种群通过几种机制失活到基态；一些种群仍然被困在 S(2)态。后两个事件可以与实验中观察到的 fs 和 ps 瞬态相关联。
