Theoretical Studies of Electronic Structure and Dynamical Aspects of Electronically Nonadiabatic Processes

理论和计算化学项目将在未来三年为约翰·霍普金斯大学的Yarkony教授提供支持。Yarkony的研究将集中在有关电子非绝热过程的电子结构方面的基本问题上。特别令人感兴趣的是圆锥交点的轨迹，特别是具有相同对称性的两个状态的轨迹。将在接下来的赠款期间研究锥形交叉点的流行和影响，以调查它们在电子非绝热过程中的作用。第二个基本问题涉及通常用于研究非绝热过程动力学的非绝热基团。虽然经常使用，但非绝热基只存在于近似意义上。导数联轴器的线积分可以用来确定导数联轴器的不可拆卸部分的大小，也就是导数联轴器中必须保持在最非绝热基础上的部分。Yarkony将使用这项技术来识别导数联轴器的不可拆卸部分可以察觉到的系统。对于这些系统，他将使用从头算的导数耦合来构建最非绝热的基团，并将结果与常用的但必然是近似的非绝热过程进行比较。这项工作有望为了解非绝热基团的性质提供基本的见解。暴露在光下的分子的化学，光化学，与基态分子的化学是根本不同的。本质上的区别在于，当分子非绝热地弛豫到基电子态时，由光激发过程产生的电子能量相互转换为振动、转动和平移能量。尽管非绝热过程无处不在，例如在视觉、光合作用和平流层臭氧降解中发生，但关于非绝热过程的许多基本问题需要解决。非绝热过程的主要驱动力之一是一种称为锥形交点的拓扑特征。曾经被认为是由于分子的特殊、对称的性质而罕见的情况，现在很清楚，就像非绝热过程本身一样，锥形交叉是无处不在的。Yarkony将使用约翰·霍普金斯大学在过去十年中开发的独特的计算机算法系统来研究与圆锥形交叉口相关的基本问题及其影响非绝热过程的方式。

The Theoretical and Computational Chemistry Program is supporting Prof. Yarkony at Johns Hopkins University over the next three years. Yarkony's research will focus on fundamental questions concerning the electronic structure aspects of electronically non-adiabatic processes. Of particular interest will be the locus of points of the conical intersection, particularly of two states of the same symmetry. The prevalence and impact of conical intersections will be studied in the ensuing grant period to investigate their role in electronically non-adiabatic processes. A second basic question concerns the diabatic bases routinely used to study the dynamics of non-adiabatic processes. Although routinely used, diabatic bases exist only in an approximate sense. Line integrals of the derivative coupling can be used to determine the size of the nonremovable part of the derivative coupling, that is the portion of the derivative coupling that must remain even in the 'most diabatic' basis. Yarkony will use this technique to identify systems for which the nonremovable part of the derivative coupling is appreciable. For these systems he will use the ab initio derivative couplings to construct the 'most diabatic' basis and compare the results with commonly used but necessarily approximate diabatization procedures. This work is expected to provide fundamental insights to the nature of diabatic bases. The chemistry of molecules exposed to light, photochemistry, is fundamentally different from the chemistry of ground state molecules. The essential difference lies in the interconversion of electronic energy created by the photoexcitation process into vibrational, rotational and translational energy as the molecule relaxes non-adiabatically to the ground electronic state. Although non-adiabatic processes are ubiquitous, occurring for example in vision, photosynthesis, and stratospheric ozone degradation, many basic questions concerning non-adiabatic processes need to be addressed. One of the principal drivers of non-adiabatic processes is a topological feature known as a conical intersection. Once thought to be rare occurrences attributable to special, symmetry, properties of a molecule, it is now clear that like non-adiabatic processes themselves conical intersections are ubiquitous. Yarkony will use a unique system of computer algorithms developed at Johns Hopkins University over the last decade to study fundamental issues related to conical intersections and the way they influence non-adiabatic processes.