Femtosecond Transition-state Dynamics
نویسندگان
چکیده
Since the early days of the transition-state theory of Eyring, Evans and Polanyi,' the fleeting nature of the state as the reaction proceeds from reagents to products has been known. The lifetime of the state is typically s, and hence to observe these transition states in real time the temporal resolution must be on the femtosecond scale. Progress has been made in probing transition states of elementary reactions and in studying the dynamics in real time.2 The objective of this account is not to review all the work done in this area (for a review, see ref. 2). Instead, I wish to discuss recent developments with particular focus on twoand one-dimensional reactions. The dimensionality (D) of the potential-energy surface (PES) determines the nature of the transition state, TS. In 1-D systems there is only one vibrational coordinate, and the motion can be mapped out as atoms recoil along this coordinate in the transition region. In 2-D (or more) systems, there may be a saddle point, and the dynamics would involve both the translational motion along the antisymmetric coordinate and vibrational motion (dynamical resonance) along the symmetric coordinate. In this case the saddle point defines clearly a TS, and the system spans both bound and repulsive features of the PES. Experiments demonstrating the dynamics in such systems are reported, and comparison with theory is made.
منابع مشابه
Reprint of: Femtosecond transition-state spectroscopy of iodine: From strongly bound to repulsive surface dynamics
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