The effect of reagent translational energy on the dynamics of the reaction O(3P)+CS(X 1Σ+)→CO(X 1Σ+)+S(3P)

Abstract

Two different regimes of collision energy are used to explore the role of additional translational energy on the dynamics of the reaction O(3P)+CS(X 1Σ+)→CO(X 1Σ+)+S(3P). Product CO rotational quantum-state population distributions for CO(v′=12, 13, and 14) are used as an indicator of the reaction dynamics, and these rotational distributions are presented for reaction of thermal reagents (at 298 K) and for translationally hot oxygen atoms formed by the 355 nm photolysis of NO2. The experimental measurements are compared with the results of quasiclassical trajectory calculations performed on an empirical London–Eyring–Polanyi–Sato potential energy surface tailored to model the observed dynamics for thermal reagents. Efficient conversion of the extra translational energy into product rotation is seen for all vibrational levels studied. The data are found to fit a simple model in which the fraction of the extra kinetic energy which appears as product rotation varies linearly with kinetic energy, and becomes unity for the fastest oxygen atoms produced by photolysis. The experimental results are interpreted in terms of an increasingly bent transition state for the reaction at higher collision energies, with the possibility of reagent reorientation towards a more linear transition state as the kinetic energy is decreased.