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Published June 4, 1998 | public
Journal Article

Femtosecond Real-Time Probing of Reactions. 23. Studies of Temporal, Velocity, Angular, and State Dynamics from Transition States to Final Products by Femtosecond-Resolved Mass Spectrometry


In this contribution, we give a full account of the approach of femtosecond, time-resolved mass spectrometry in molecular beams for the studies of the elementary steps of complex reactions and the application to different systems. The level of complexity varies from diatomics to polyatomics, from direct-mode to complex-mode, from one-center, to two-center, to four-center, and from uni- to bimolecular reactions. The systems studied are iodine, cyanogen iodide, methyl iodide, iodobenzene, 1,2-diiodotetrafluoroethane, mercury iodide, benzene· iodine complexes, and methyl iodide dimers. By resolving the femtosecond dynamics and simultaneously observing the evolution of velocity, angular, and state distribution(s) of the reaction, we are able to study multiple reaction paths, the nature of transition-state geometry and dynamics, coherent wave-packet motion, evolution of energy disposal, and the nonconcerted motion in multicenter reactions. These phenomena and concepts are elucidated in dissociation, elimination, and charge-transfer reactions and in the inelastic and reactive pathways of bimolecular reactions. Theoretical phenomenology, using frontier orbitals and molecular dynamics, are invoked to provide a relationship between the observed dynamics and molecular structures.

Additional Information

© 1998 American Chemical Society. Received: December 15, 1997; In Final Form: January 26, 1998. Publication Date (Web): March 21, 1998. This work was supported by a grant from the National Science Foundation, the Air Force Office of Scientific Research, and the Office of Naval Research. We thank Dr. P. Y. Cheng for his effort and stimulating discussions, especially when experiments on the charge-transfer systems and iodobenzene were being conducted.

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