Theoretical Study of Photodissociation Dynamics in the Gaseous and Condensed Phases

托莱多大学的郭华是由美国国家科学基金会理论与计算化学计划资助的化学反应动力学理论研究人员。这项工作的重点是光解的研究；特别是，时间相关的量子力学将用于研究小分子的光解动力学。这些过程将在气相、表面和溶液中进行研究。为了处理后两种情况的问题，将发展一种新的理论方法，即量子方法和经典方法的混合方法。通过这种混合方法，分子反应的量子特性得到了适当的处理，但介质、底物或溶剂的影响也包括在内。对于气相研究，将处理一些中等大小的多原子分子；这些包括稀有气体配合物和甲基配合物的Ryderg激发态。一般来说，光诱导化学的动力学，特别是光解的动力学，取决于系统中原子之间相互作用能量的细节；也就是在势能面的细节上。然而，将这个表面的特征与反应产物的同一性以及这些产物的能量分布联系起来并不简单。本项目所进行的光解研究将加深对相关关系的理解。特别是，这项工作的两个方面有助于确保它将对这一重要的科学目标产生相当大的影响。首先，正在进行的工作是与实验人员密切接触，经常是合作进行的。因此，用于获得潜在势能面的近似以及用于研究反应随时间变化的量子特征的近似都可以得到验证。其次，所研究的系统是经过精心选择的，以产生重要和有用的信息。它们足够小，可以用于高精度的量子力学处理，但又足够大，可以包含化学键和其他与光化学中更一般问题相关的特征。

Hua Guo at the University of Toledo is supported by the NSF Theoretical and Computational Chemistry Program for theoretical investigations of chemical reaction dynamics. The concern of this work is the study of photodissociation; in particular, time dependent quantum mechanics will be used to study the photodissociation dynamics of small molecules. These processes will be studied in the gas phase, on surfaces, and in solution. In order to treat problems in the later two cases, a new theoretical procedure will be developed which is a hybrid approach combining quantum and classical methods. With this hybrid approach, the quantum features of the molecular reaction are properly addressed but the effects of the medium, substrate or solvent, are included. For the gas phase studies, a few modest size polyatomic molecules will be treated; these include rare gas complexes and Ryderg excited states of methyl complexes. The dynamics of photo-induced chemistry, in general, and of photodissociation, in particular, depend on the details of the interaction energies among the atoms in the system; i.e., on the details of the potential energy surfaces. However, it is not simple to relate the features of this surface to the identity of the reaction products and to the energy distribution over these products. The studies of photodissociation being carried out in this project will enhance the understanding of the relevant relationships. In particular, two aspects of the work help to insure that it will have considerable impact on this important scientific goal. First, the work is being carried out is close contact and, often, in collaboration with experimentalists. Because of this, the approximations used to obtain the underlying potential energy sufaces as well as those used to study the time dependent quantum features of the reaction can be validated. Second, the systems being studied are carefully chosen to yield important and useful information. They are sufficiently small to be tractable for high accuracy quantum mechanical treatments yet sufficiently large to contain chemical bonds and other features relevant to more general problems in photochemistry.