Institut de Química Computacional, Departament de Química, Universitat de Girona, Campus Montilivi, 17071 Girona, Spain.
Phys Chem Chem Phys. 2010 May 21;12(19):4949-58. doi: 10.1039/c001556c. Epub 2010 Mar 29.
The role of the seam of intersection between the lowest (pi,pi*) and (n,pi*) excited states in the decay of electronically excited singlet thymine has been investigated with ab initio complete active space self-consistent field (CASSCF) calculations and direct dynamics variational multiconfiguration Gaussian (DD-vMCG) quantum dynamics on the full-dimensional CASSCF surface, with 39 degrees of freedom. The seam has a sloped-to-peaked topography, and the dynamics at the different segments of the seam have been studied by varying the initial conditions of the propagation. When the wave packet is directed to the peaked segments, part of it traverses the seam, stays on the (pi,pi*) state and heads towards decay to the ground state. In contrast to this, when the wave packet is driven to sloped seam segments it bounces back to the minimum of the (pi,pi*) state. Significant population transfer to the (n,pi*) state is observed in both cases. The results suggest that a sloped-to-peaked topography can be used to control photochemical reactivity, by driving the wave packet to different regions of the seam where a different outcome of the propagation can be expected.
用从头计算完全活性空间自洽场 (CASSCF) 计算和全维 CASSCF 表面上的直接动力学变分多组态高斯 (DD-vMCG) 量子动力学，研究了最低（π，π*）和（n，π*）激发态的交界缝在电子激发态胸腺嘧啶衰变中的作用，自由度为 39。交界缝具有倾斜到峰值的地形，通过改变传播的初始条件研究了交界缝不同部分的动力学。当波包指向峰值部分时，其中一部分穿过交界缝，停留在（π，π*）态上，并朝向基态衰变。与此相反，当波包被驱动到倾斜的交界缝部分时，它会反弹回（π，π*）态的最低点。在这两种情况下都观察到向（n，π*）态的显著转移。结果表明，通过将波包驱动到交界缝的不同区域，可以使用倾斜到峰值的地形来控制光化学反应性，在不同区域的传播可以预期不同的结果。
