基态激发态roaming机理的理论研究

项目名称： 基态激发态roaming机理的理论研究

项目编号： No.21473227

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 数理科学和化学

项目作者： 肖红艳

作者单位： 中国科学院理化技术研究所

项目金额： 85万元

中文摘要： 过渡态理论是化学反应动力学领域最基本的理论之一，在阐明化学反应机理方面起到非常重要的作用。然而，2004年光解H2CO发现一个不同于过渡态的机理，被称作roaming机理，引起人们广泛关注。尤其是最近光解NO3自由基发现激发态上也存在roaming机理。大量研究表明roaming机理是普遍存在，这激发了人们对过渡态理论不足之处的思考。本项目以光解羰基和硝基化合物为例，全面系统地研究基态激发态roaming机理。我们将使用全局反应路径策略搜索所有反应路径；MS-CASPT2方法再次优化和检查自动搜索的反应路径；非绝热动力学模拟研究光化学反应的动力学特征；总结这类羰基和硝基化合物光解离过程中基态激发态roaming反应路径的特征和本质。本项目的成功开展，不仅是对羰基和硝基化合物光解离机理的全面解析，更是对基态激发态上roaming反应机理的深入认识。同时也将为新的化学反应理论发展提供理论基础。

中文关键词： 光化学；roaming机理；激发态；多态完全活化空间二阶微扰理论；非绝热动力学

英文摘要： Transition state theory is one of the most fundamental theories of chemical reaction dynamics, which plays a very important role in understanding chemical reaction mechanism. However, in 2004, the study of H2CO photodissociation discovered a new mechanism, named roaming mechanism, which is different from the conventional transition state mechanism. Since this discovery it has aroused widespread concern in both experiment and theory. Especially, the excited-state roaming dynamics in NO3 photolysis was also found and reported recently. Till now many studies show that the roaming mechanism is ubiquitous. It has to arouse researchers to think the inadequacy of the present transition state theory. In this project we take the photodissociations of carbonyl compounds and nitro compounds as examples to comprehensively elucidate the ground- and excited-state roaming reaction mechanisms. We will use the global reaction route mapping (GRRM) to search all the reaction pathways of carbonyl compounds and nitro compounds on the ground and excited states; MS-CASPT2 method to re-optimize and check all the pathways searched automatically ; non-adiabatic dynamics simulations to study the dynamic properties of the photochemical reactions; analyzing the characteristics and natures of the ground- and excited-state roaming mechanisms of the photodissociations of carbonyl compounds and nitro compounds based on the electronic structure calculations and non-adiabatic dynamics simulations. As a result, this study will not only elucidate the comprehensive photodissociation mechanisms of carbonyl compounds and nitro compounds, but also have a profound insight into understanding the ground- and excited-state roaming mechanisms. At the same time, it will provide the theoretical basis for the development of new chemical reaction theories.

英文关键词： photochemistry;roaming mechanism;excited state;MS-CASPT2;non-adiabatic dynamics