Coe Joshua D, Ong Mitchell T, Levine Benjamin G, Martínez Todd J
Department of Chemistry, Beckman Institute, and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, 600 South Mathews AVenue, Urbana, Illinois 61801, USA.
J Phys Chem A. 2008 Dec 11;112(49):12559-67. doi: 10.1021/jp806072k.
We discuss the connectivity of intersection spaces and the role of minimal energy points within these intersection spaces (minimal energy conical intersections or MECIs) in promoting nonadiabatic transitions. We focus on malonaldeyde as a specific example, where there is a low-lying three-state conical intersection. This three-state intersection is the global minimum on the bright excited electronic state, but it plays a limited role in population transfer in our ab initio multiple spawning (AIMS) simulations because the molecule must traverse a series of two-state conical intersections to reach the three-state intersection. Due to the differences in seam space dimensionality separating conventional (two-state) and three-state intersections, we suggest that dynamical effects arising directly from a three-state intersection may prove difficult to observe in general. We also use a newly developed method for intersection optimization with geometric constraints to demonstrate the connectivity of all the stationary points in the intersection spaces for malonaldehyde. This supports the conjecture that all intersection spaces are connected, and that three-state intersections play a key role in extending this connectivity to all pairs of states, e.g. the S1/S0 and S2/S1 intersection spaces.
我们讨论了交叉空间的连通性以及这些交叉空间内的最小能量点（最小能量锥形交叉点或MECIs）在促进非绝热跃迁中的作用。我们以丙二醛作为具体例子，其中存在一个低能三态锥形交叉点。这个三态交叉点是明亮激发电子态上的全局最小值，但在我们的从头算多重Spawn（AIMS）模拟中，它在布居转移中所起的作用有限，因为分子必须穿过一系列二态锥形交叉点才能到达三态交叉点。由于分隔常规（二态）和三态交叉点的接缝空间维度存在差异，我们认为一般来说，直接由三态交叉点产生的动力学效应可能难以观测到。我们还使用了一种新开发的具有几何约束的交叉点优化方法，来证明丙二醛交叉空间中所有驻点的连通性。这支持了这样的推测：所有交叉空间都是连通的，并且三态交叉点在将这种连通性扩展到所有状态对（例如S1/S0和S2/S1交叉空间）方面起着关键作用。
