Excited-State Relaxation of Hydrated Thymine and Thymidine Measured by Liquid-Jet Photoelectron Spectroscopy: Experiment and Simulation
Excited-State Relaxation of Hydrated Thymine and Thymidine Measured by Liquid-Jet Photoelectron Spectroscopy: Experiment and Simulation
复制标题
DOI：
10.1021/ja511108u
复制
发表时间：
2015-03-04
影响因子：
15
通讯作者：
Luebcke, Andrea
中科院分区：
文献类型：
--
作者：
Buchner, Franziska;Nakayama, Akira;Luebcke, Andrea
对水溶液中的胸腺嘧啶和胸苷进行时间分辨光电子能谱，研究这些分子的激发态弛豫动力学。我们发现两个贡献与最近的激发态QM/MM分子动力学模拟（J. Chem. Phys. 2013，139，214304）。计算了受激π π * 态电离能沿沿着QM/MM分子动力学轨道的时间演化，并与实验结果相一致，其中两个贡献对应于π π * 态中涉及与基态不同圆锥相交的弛豫路径.理论计算还表明，电离从n π * 状态是可能的，在给定的光子能量，但我们还没有发现任何实验指示信号从n π * 状态。与目前公认的弛豫机制相反，我们认为，n π * 状态不参与胸腺嘧啶在水溶液中的弛豫过程。
Time-resolved photoelectron spectroscopy is performed on thymine and thymidine in aqueous solution to study the excited-state relaxation dynamics of these molecules. We find two contributions with sub-ps lifetimes in line with recent excited-state QM/MM molecular dynamics simulations (J. Chem. Phys. 2013, 139, 214304). The temporal evolution of ionization energies for the excited pi pi* state along the QM/MM molecular dynamics trajectories were calculated and are compatible with experimental results, where the two contributions correspond to the relaxation paths in the pi pi* state involving different conical intersections with the ground state. Theoretical calculations also show that ionization from the n pi* state is possible at the given photon energies, but we have not found any experimental indication for signal from the n pi* state. In contrast to currently accepted relaxation mechanisms, we suggest that the n pi* state is not involved in the relaxation process of thymine in aqueous solution.