Theoretical Models for Photoisomerization Dynamics

内华达大学里诺分校化学系的John H. Frederick教授获得了美国国家科学基金会理论与计算化学项目的资助，研究振动光谱学和激发态分子动力学。该基金支持的工作主要集中在光诱导反应上，这些反应可以在几种气相分子中形成不同稳定几何形状的异构体。正在研究的分子是一类具有共轭系统的分子的代表。研究的第一步是结合实验数据和从头算理论数据构建相互作用能面描述。然后，利用准经典和量子力学方法研究了从基态到第一激发态的激发和退激返回基态的动力学。这些研究可能导致控制反应进行的方式和形成的不同异构体的数量的方法。共轭pi-系统分子的光化学对于许多自然过程，如视觉和光合作用，以及有机导体都是至关重要的。这门课上的许多分子都被实验学家和理论家广泛研究过，对这些系统的性质也有很多了解。然而，光化学转化发生的动力学机制仍未完全了解。这项资助下的工作正在解决这个缺失的环节。

Professor John H. Frederick at the Chemistry Department of the University of Nevada, Reno is supported by a grant from the Theoretical and Computational Chemistry Program at NSF to study vibrational spectroscopy and excited state molecular dynamics. The work supported under this grant is focussed on light induced reactions that form isomers, different stable geometries, in several gas phase molecules. The molecules that are being studied are representative of a class of molecules which have conjugated pi-systems. The first step in the studies is to use a combination of experimental data and ab initio theoretical data to construct descriptions of the interaction energy surfaces. Then, the dynamics of excitation from the ground to the first excited state and de-excitation back to the ground state are studied using both quasiclassical and quantum mechanical methods. These studies may lead to methods to control the way in which the reactions proceed and the amounts of different isomers which are formed. The photochemistry of molecules with conjugated pi-systems is of central importance for many natural processes, such as vision and photosynthesis, and for organic conductors. Many molecules in this class have been extensively studied by experimentalists and by theorists and much is known about the properties of these systems. However, the dynamical mechanisms by which photochemical transformations occur are still not fully understood. The work under this grant is addressing this missing link.