The photochemistry of carbonyl sulfide (OCS) adsorbed to small silverclusters is shown to exhibit a striking odd–even dependence on the number of Ag atoms in the cluster. OCS is found to desorb nondissociatively from even numbered silverclusters. In contrast, on odd silverclusters, a new product channel corresponding to AgₙS is observed. Parallels are found with the photochemistry of adsorbates on extended surfaces. Cross-section measurements for OCS desorption from Ag₁₀ and wavelength-dependent measurements of OCS dissociation on Ag₉ both indicate that electronic excitation of the cluster initiates chemistry, analogous to substrate mediated surface photochemistry. The size dependence is reasonably explained in terms of a charge-transfer mechanism involving an ion-pair state of the AgₙOCS complex.
The Journal of Chemical Physics109, no. 6 (4 May 1998): 2474–.