The role of rotational excitation in the activated dissociative chemisorption of vibrationally excited methane on Ni(100)

We have measured the sticking probability of methane excited to v=1 of the nu (3) antisymmetric C-H stretching vibration on a clean Ni(100) surface as a function of rotational state (J=0, 1, 2 and 3) and have investigated the effect of Coriolis-mixing on reactivity. The data span a wide range of kin etic energies (9-49 kJ mol(-1)) and indicate that rotational excitation doe s not alter reactivity by more than a factor of two, even at low molecular speeds that allow for considerable rotation of the molecule during the inte raction with the surface. In addition, rotation-induced Coriolis-splitting of the nu (3) mode into F+, F-0 and F- states does not significantly affect the reactivity for J=1 at 49 kJ mol(-1) translational energy, even though the nuclear motions of these states differ. The lack of a pronounced rotati onal energy effect in methane dissociation on Ni(100) suggests that our pre vious results for (v=1, nu (3), J=2) are representative of all rovibrationa l sublevels of this vibrational mode. These experiments shed light on the r elative importance of rotational hindering and dynamical steering mechanism s in the dissociative chemisorption on Ni(100) and guide future attempts to accurately model methane dissociation on nickel surfaces.