John Frederick is supported by a grant from the Theoretical and Computational Chemistry Program to continue his studies of the dynamics of photoisomerization and nonadiabatic relaxation processes. The objective of this work is to develop detailed models for the electronic and vibrational dynamics of the photoinduced processes in the hexatriene and octatetraene systems. Quantitatively accurate potential energy surfaces for the lowest three singlet states of these systems and the nonadiabatic coupling between them will be derived using a combination of high-level ab initio calculations and spectroscopic data. Ultrafast internal conversion and isomerization processes in these systems will be studied using both quasiclassical and quantum dynamics. A number of specific questions regarding the photochemistry and photophysics of these systems will be elucidated. The photochemistry of polyenes is of central importance in a number of natural processes, such as vision and photosynthesis, and in the development of organic materials with conducting and photochromic properties. The proposed work has a potential for significant scientific impact in providing a molecular level interpretation of these phenomena.
