Barrierless reactions between two closed-shell molecules. II. Dynamics of F₂ + CH₃SSCH₃ reaction

A second example of a barrierless reaction between two closed-shell molecules is reported. The reaction F2 + CH3 SSCH3 has been investigated with crossed molecular beam experiments and ab initio calculations. Compared with previous results of the F2 + CH3 SCH3 reaction [J. Chem. Phys. 127, 101101 (2007); J. Chem. Phys. 128, 104317 (2008)], a new product channel leading to CH3 SF+ CH3 SF is observed to be predominant in the title reaction, whereas the anticipated HF+ C2 H5 S2 F channel is not found. In addition, the F+ C2 H6 S2 F product channel, the analog to the F+ C2 H6 SF channel in the F2 + CH3 SCH3 reaction, opens up at collision energies higher than 4.3 kcal/mol. Angular and translational energy distributions of the products are reported and collision energy dependences of the reaction cross section and product branching ratio are shown. The reaction barrier is found to be negligible (<1 kcal/mol). Multireference ab initio calculations suggest a reaction mechanism involving a short-lived intermediate which can be formed without activation energy.