Seminars Archive
Quantum State Resolved Studies of Gas/Surface Reaction Dynamics
Abstract
Monday, July 5, 2004, 16:30
Seminar Room, ground floor, Building "T"
Sincrotrone Trieste, Basovizza
Quantum State Resolved Studies of Gas/Surface Reaction
Dynamics
Rainer D. BECK
( Laboratoire de Chimie Physique Moleculaire (LCPM)
Ecole Polytechnique Fdrale de Lausanne (EPFL))
Abstract
Laser light is a powerful tool for detailed experimental studies of
chemical reactions at the gas/surface interface. It can be used to prepare
molecules incident on a solid surface in specific quantum states for state
resolved reactivity measurements [1]. We have used this technique to measure
state resolved reaction cross sections for the dissociative chemisorption
of methane (CH4 and its isotopomers) on single crystal surfaces of nickel
as a function of incident kinetic energy. The results provide a comparison
of the efficacy of energizing different degrees of freedom of the incident
molecule for crossing the reaction barrier [2]. Different cross sections
for nearly isoenergetic vibrational states clearly demonstrates the presence
of mode specificity in this gas - surface reaction. For CD2H2, we observed
up to a factor of 5 greater reaction probability with two quanta of excitation
in one C-H bond versus one quanta in each of two C-H bonds [3] . These
results clearly exclude the possibility of statistical models correctly
describing the mechanism of this process and emphasize the importance of
full-dimensional calculations of the reaction dynamics.
[1] M.P. Schmid, P. Maroni, R.D. Beck and T.R. Rizzo, Rev. Sci. Inst.,
74, 4110 (2003)
[2] M.P. Schmid, P. Maroni, R.D. Beck and T.R. Rizzo, J. Chem. Phys.
117, 8603 (2002)
[3] R.D. Beck, P. Maroni, D. C. Papageorgopoulos, T.T. Dang, M.P. Schmid,
T.R. Rizzo, Science, 302, 98 (2003)
