AVS 56th International Symposium & Exhibition
    Surface Science Wednesday Sessions
       Session SS2-WeA

Paper SS2-WeA10
Surface Dynamics of Molecules in Single Internal (Vibrational and Rotational) States

Wednesday, November 11, 2009, 5:00 pm, Room N

Session: Surface Physics, Single Particle Imaging
Presenter: A.L. Utz, Tufts University
Authors: V.L. Campbell, Tufts University
N. Chen, Tufts University
A.L. Utz, Tufts University
Correspondent: Click to Email
Beam-surface scattering studies of molecules prepared in a single internal quantum state provide a high level of control over the energetics and internal motion of the gas-phase reagent. Varying the identity of the laser-excited state permits a systematic survey of how vibrational excitation in the gas-phase reagent (bending or stretching excitation) impacts reactivity and reveals that both vibrational mode-selective and bond-selective chemistry is possible in a gas-surface reaction. Recently, we have begun to exploit the energetic control this approach offers to probe the dynamics of other energetic degrees of freedom. For example, state resolved reactivity measurements (S0 vs. Etrans) of CH4 dissociation on Ni(111) show that the shape of the sticking curve changes as a function of surface temperature. This change likely results from the modulation of the effective barrier to reaction along the translational energy coordinate as a function of surface atom position. Our experimental results are consistent with recent theoretical studies that point to an important role for surface atom motion in promoting dissociative chemisorption on Ni and Pt surfaces. The presentation will focus on our use of state-selected reagents to probe dynamics associated with other energetic degrees of freedom, such as surface atom motion. It will also describe advances in our experimental methods for acquiring these state-resolved data. These advances are transforming our ability to perform state-resolved measurements and will enable our extension of these methods to a much wider array of chemical systems.