Role of Structural Fluctuation in a Surface Reaction Studied by Scanning Tunneling Microscopy: The $\mathrm{C}\mathrm{O}+\mathrm{O}\to {\mathrm{C}\mathrm{O}}_2$ Clean-Off Reaction on Ag(110)-($2\times 1$)-O

The kinetics of the clean-off reaction of O adatoms by CO on Ag(110)-($2\times 1$)-O is investigated by scanning tunneling microscopy. The reaction is accelerated in the lower O coverage range where AgO chains with ($n\times 1$) ($n\ge 4$) configurations show significant structural fluctuation. Simulations based on the Ising model are used to provide a quantitative understanding of the acceleration, which originates from the dynamical formation of active O adatoms by fluctuation of AgO chains.