Femtosecond real-time probing of reactions. XXI. Direct observation of transition-state dynamics and structure in charge-transfer reactions

This paper in the series gives our full account of the preliminary results reported in a communication [Cheng, Zhong, and Zewail, J. Chem. Phys. 103, 5153 (1995)] on real‐time femtosecond (fs) studies of the transition state of charge‐transfer (CT)reactions, generally described as harpooning reactions. Here, in a series of experimental studies in a molecular beam, and with the help of molecular dynamics, we elucidate the microscopic elementary dynamics and the structure of the transition states for the isolated, bimolecular reaction of benzenes (electron donor) with iodine (electron acceptor). The transition state is directly reached by fs excitation into the CT state of the complex Bz⋅I_2, and the dynamics is followed by monitoring the product build up or the initial transition‐state decay