Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published December 1, 1993 | public
Journal Article

Femtosecond real-time probing of reactions. 12. Vectorial dynamics of transition states


Femtosecond time-resolved techniques with KETOF (kinetic energy time-of-flight) detection in a molecular beam are developed for studies of the vectorial dynamics of transition states. Application to the dissociation reaction of IHgI is presented. For this system, the complex [I•••Hg•••I]^(≠*) is unstable and, through the symmetric and asymmetric stretch motions, yields different product fragments: [I•••Hg•••I]^(≠*) → HgI(X^2Z^+) + I(^2P_(3/2)) [or I^*(^2P_(l/2)]; (la); [I•••Hg•••I]^(≠*)(^1S_0) + I(^2P_(3/2)) + I(^2P_(3/2)) [or I^*(^2P_(1/2))] (lb). These two channels, (la) and (1 b), lead to different kinetic energy distributions in the products. It is shown that the motion of the wave packet in the transition-state region can be observed by MPI mass detection; the transient time ranges from 120 to 300 fs depending on the available energy. With polarized pulses, the vectorial properties (transition moments alignment relative to recoil direction) are studied for fragment separations on the femtosecond time scale. The results indicate the nature of the structure (symmetry properties) and the correlation to final products. For 311-nm excitation, no evidence of crossing between the I and I^* potentials is found at the internuclear separations studied. (Results for 287-nm excitation are also presented.) Molecular dynamics simulations and studies by laser-induced fluorescence support these findings.

Additional Information

© 1993 American Chemical Society. Received: September 9, 1993. Abstract published in Advance ACS Abstracts. November 1, 1993. Deutsche Forschungsgemeinschaft (DFG) postdoctoral fellow. Contribution No. 8847.

Additional details

August 20, 2023
October 20, 2023