Abstract
Detailed insight into chemical reaction dynamics can be obtained by probing the effect of mode-specific vibrational excitation. Suppression or enhancement of reactivity is possible as is already known from the Polanyi rules. In the reaction F– + CH3I, we found vibrational enhancement, suppression, and spectator mode dynamics in the four different reaction channels. For this system we have probed the influence of symmetric CH-stretching vibration over a collision energy range of 0.7–2.3 eV. Proton transfer is significantly enhanced, while for the nucleophilic substitution channel the spectator mode dynamics at lower collision energies unexpectedly move toward enhancement at higher collision energies. In contrast, for two halide abstraction channels, forming FI– and FHI–, we found an overall suppression, which stems mainly from a suppression of the FHI– product. We compare these results to quasiclassical trajectory calculations and with the sudden vector projection model.
Highlights
Detailed insight into chemical reaction dynamics can be obtained by probing the effect of mode-specific vibrational excitation
A central goal of physical chemistry is to describe chemical reactions on a fundamental level. Such descriptions include atomic-level mechanisms, the collision energy dependence of the reactivity, and the energy partitioning among different reaction products
A main focus has been on thhaelidweesllw-sittuhdipeadrtFial+lyHd2euretearcatitoedn9,m10eathsawneellaansdownarteear.c1t1i−o1n4s of In the case of atomic O and F reacting with CHD3, the observed enhancement and suppression due to C−H stretching vibration could be assigned in comparison with high-level quasi-classical trajectory (QCT) calculations to steric effects.[15−22] These effects are caused by a change in the long-range interaction, due to a change in the dipole moment caused by the vibration, that steers the approaching reactants into or away from the favored geometry
Summary
Detailed description of the experimental procedures; differential cross sections for the halide abstraction channel leading to the FI−
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