Without collisions there is no surface reaction. Molecular collisions are an inherent part of surface reactions. They cause molecular and geometrical rearrangements, induce energy transfer to specific quantum states, or simply cause a molecule to break apart. The stereodynamics of the reactants, the orientation and the movement of molecule in 3D space, plays an important role in surface reactions. As with astronauts approaching their space station, some maneuvers are more effective than others for successful docking. Implementing computation-based materials/reaction design (CMD®/CRD®) techniques (cf., e.g., [1]), we have explored this inherent orientation dependence of gas-surface reaction dynamics, e.g., in increasing the ortho-para(o-p) H2 conversion yield (cf., e.g., [2]), utilizing concepts such as Dynamical Quantum Filtering (cf., e.g., [2-7], Steering (cf., e.g., [2-7]) , and Steric Effects(cf., e.g., [2]). Earlier, we have shown theoretically [6] that (later confirmed experimentally [8]) not only is the H2(D2)-surface interaction (viz., the H2(D2) dissociative adsorption dynamics) strongly dependent on the orientation of the impinging H2(D2), but also that the orientation dependence is strongly sensitive to the kinetic energy of the impinging H2(D2). At the meeting, we will show how would also be observable for the reverse process of associative desorption, viz., the angular distribution of the desorbing H2(D2). These results hint at possible means of probing local surface reactivity [7].
[1] H. Kasai et al., (Eds.), Introduction to Computational Materials Design (CMD®) - From Basics to Actual Applications - (Osaka Univ. Press, Osaka, 2005).
[2] H. Kasai, W.A. Diño, R. Muhida, Prog. Surf. Sci. 72 (2003) 53.
[3] W.A. Diño, H. Kasai, A. Okiji, Surf. Sci. 418 (1998) L39.
[4] W.A. Diño, H. Kasai, A. Okiji, Prog. Surf. Sci. 63 (2000) 63.
[5] Y. Miura, H. Kasai, W.A. Diño, J. Phys.: Condens. Matter 14 (2002) L479.
[6] W.A. Diño, H. Kasai, A. Okiji, Phys. Rev. Lett. 78 (1997) 286.
[7] W.A. Diño, J. Phys.: Condens. Matter 14 (2002) 4379.
[8] H. Hou et al., Science 277 (2002) 80. |