AVS 46th International Symposium
    Surface Science Division Wednesday Sessions
       Session SS2-WeA

Paper SS2-WeA9
Vibrational-State-Selected Studies of Gas-Surface Dynamics

Wednesday, October 27, 1999, 4:40 pm, Room 607

Session: Gas-Surface Dynamics
Presenter: A.L. Utz, Tufts University
Authors: A.L. Utz, Tufts University
L.B.F. Juurlink, Tufts University
R.R. Smith, Tufts University
P.R. McCabe, Tufts University
C.L. DiCologero, Tufts University
Correspondent: Click to Email
A recently developed experimental technique uses state-resolved infrared laser excitation to probe dissociative chemisorption dynamics with quantum state resolution. We combine a supersonic molecular beam source, infrared laser excitation of methane molecules in the beam, and UHV surface spectroscopies to quantify the reactivity of gas-phase reagents excited to single, selected vibrational states. This approach permits independent and precise control over the translational and vibrational energy content of gas-phase reactants, as well as the character of their vibrational motion. We report on our use of this approach to unravel the dissociative chemisorption dynamics of methane on Ni(100). We find that methane molecules excited to the v=1 level of the antisymmetric C-H stretching vibration, @nu@@sub 3@, are up to 1600 times more reactive than are molecules in the v=0 level. Over a translational energy range from 16 to 68 kJ/mol, the sticking probability for these molecules increases from 3x10@super -5@ to 2x10@super -2@, which indicates that the @nu@@sub 3@ state is only responsible in part for the reactivity of a thermal distribution of vibrational states. We will also compare the efficacy of @nu@@sub 3@ excitation with other coordinates for energy deposition in the methane/nickel system.