Product Vibrational State-to-State Correlation in the F + SiH4 → HF(vHF) + SiH3 (0v20) Reaction: A Crossed Molecular Beam Ion-Imaging Study

The dynamics of the F + SiH(4) --> HF + SiH(3) reaction has been studied using the crossed molecular beam technique with slice imaging at collision energies from 1.25 to 8.17 kcal/mol. The product silyl radical, SiH(3)(v(2) = 0-5), was detected using the (2 + 1) resonance enhanced multiphoton ionization technique. The product velocity distributions and angular distributions of this reaction were obtained from the recorded images. Experimental results show that the silyl radical product is mainly forward scattered relative to the silane beam direction, and the majority of the available energy was partitioned into the vibration of the HF product. The state-to-state correlation between the two reaction products, SiH(3) and HF, was also determined. In addition, we found that the reaction cross section goes down as the collision energy increases. From these results, we conclude that the F + SiH(4) --> HF + SiH(3) reaction proceeds through a direct abstraction mechanism with little or no reaction barrier.