  We use multi-scale modeling to analyze laser-induced fluorescence (LIF)
measurements of the CO oxidation reaction over Pd(100) at near-ambient reaction
conditions. Integrating density-functional theory based kinetic Monte Carlo
simulations of the active catalyst into fluid-dynamical simulations of the mass
transport inside the reactor chamber we calculate the reaction product
concentration directly above the catalyst surface. Comparing corresponding data
calculated for different surface models against the measured LIF signals we can
discriminate the one that predominantly actuates the experimentally measured
catalytic activity. For the probed CO oxidation reaction conditions the
experimental activity is due to pristine Pd(100), possibly coexisting with
other (oxidic) domains on the surface.
