Differential cross sections for O(3P)+alkane reactions by direct imaging

We report a crossed molecular beam study of the reaction of O(P-3) with cyclohexane with velocity map imaging of the cyclohexyl radical product using single photon ionization. The results represent the first direct measurement of the differential cross sections for ground state oxygen atom reactions with alkanes. The experimental approach has the advantage that the collision energy is not only well defined but also continuously tunable in a reasonable range. The results show that at 5.8 kcal/mol collision energy the products are mainly backward scattered, clearly confirming the anticipated rebound reaction mechanism. More surprising is the large fraction, nearly 60%, of the available energy partitioned into the internal degrees of freedom of the products. (C) 2002 American Institute of Physics.