Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany.
Chemphyschem. 2011 Jul 11;12(10):1989-98. doi: 10.1002/cphc.201001054. Epub 2011 Jun 14.
The photoinduced nonadiabatic decay dynamics of 9H-adenine (hereafter, adenine) in aqueous solution were investigated by surface-hopping simulations within a quantum mechanical/molecular mechanical (QM/MM) framework. The QM subsystem (adenine) was treated at the semiempirical OM2/MRCI level, whereas the MM solvent (water) was described by the TIP3P force field model. Classical molecular dynamics (MD) simulations were used to generate snapshots with different solvent configurations and geometries. For a representative number of these snapshots, the energy minima of the lowest electronic states and the most important conical intersections were located by QM/MM geometry optimization. Surface-hopping QM/MM MD simulations were performed for all selected snapshots to study the nonadiabatic dynamics after photoexcitation, including the two lowest excited singlet states, which are both populated in the initial photoexcitation due to strong vibronic coupling in the Franck-Condon region. The simulations yield ultrafast S(2)-S(1) decay within 40 fs and S(1)-S(0) internal conversion to the ground state within 410 fs, which is consistent with recent experimental results from time-resolved spectroscopy.
在量子力学/分子力学 (QM/MM) 框架内，通过表面跳跃模拟研究了 9H-腺嘌呤（以下简称腺嘌呤）在水溶液中的光诱导非绝热衰减动力学。QM 子系统（腺嘌呤）在半经验 OM2/MRCI 水平上进行处理，而 MM 溶剂（水）则用 TIP3P 力场模型描述。经典分子动力学（MD）模拟用于生成具有不同溶剂构型和几何形状的快照。对于这些快照中的代表性数量，通过 QM/MM 几何优化确定了最低电子态的能量极小值和最重要的锥形交叉点。对所有选定的快照进行表面跳跃 QM/MM MD 模拟，以研究光激发后的非绝热动力学，包括最初光激发中由于 Franck-Condon 区域中的强振子耦合而都有贡献的两个最低激发单重态。模拟得出超快 S(2)-S(1) 衰减在 40 fs 内，S(1)-S(0) 内转换到基态在 410 fs 内，这与最近的时间分辨光谱实验结果一致。
