Conical Intersections and Nuclear Dynamics: A New Look at an Old Problem

约翰霍普金斯大学的David Yarkony得到了理论和计算化学计划的支持，该计划研究电子非绝热过程，在该过程中，核运动不限于单一的Born-Oppenheimer势能面。锥形交点在非绝热动力学中所起的作用是一个特别关注的问题。对于具有奇数个电子的系统，将开发形式和计算工具来发展自旋非守恒、电子非绝热过程的完全绝热图像。这些工具将被扩展到包括自旋-轨道相互作用的锥形交叉点的位置和特征，以便处理最一般的情况。首次确定了这种锥形相交接缝的轨迹。将研究分子氢与基态和激发态的OH和SH自由基的反应，以解决增加自旋-轨道耦合的影响。此外，电子激发的OClO、OBrO以及最终的OIO的预解离也将被考虑。这项研究有望对锥形交叉口的局部地形与非绝热事件的结果之间的关系有一个更清晰的认识。了解分子势能表面交叉对于描述涉及电子激发态的化学反应至关重要。在量子化学中描述这个主题的任务是极其困难的，而且很可能在这个项目中取得重大进展。成功的结果将对光吸收引发的化学反应的表征产生重大影响。

David Yarkony of Johns Hopkins University is supported by the Theoretical and Computational Chemistry Program to study electronically nonadiabatic processes, in which nuclear motion is not restricted to a single Born-Oppenheimer potential energy surface. The role played by conical intersections in nonadiabatic dynamics is a particular focus. The formal and computational tools to develop a fully adiabatic picture of a spin nonconserving, electronically nonadiabatic process for a system with an odd number of electrons will be developed. These tools will be extended to locate and characterize conical intersections with the spin-orbit interaction included in order to treat the most general situation. For the first time, the locus of this type of conical intersection seam will be determined. The reactions of molecular hydrogen with both ground and excited state OH and SH radicals will be investigated to address the effect of increasing spin-orbit coupling. As well, the predissociation of electronically excited OClO, OBrO, and ultimately OIO will be considered. A clearer picture of the relation between the local topography of a conical intersection and the outcome of the nonadiabatic event is expected to emerge from this research. Understanding molecular potential energy surface crossings is crucially important for describing chemical reactions that involve electronically excited states. The task of describing this topic in quantum chemistry its extremely difficult, and likely to be advanced significantly in this project. Successful outcomes will have a major impact on the characterization of chemical reactions initiated by light absorption.