Laser-induced molecular desorption from size-selected nickel cluster carbonyl ions: Kinetics of the adsorption–desorption equilibrium

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Abstract
Gas phase reactivity of size-selected nickel cluster ions with carbon monoxide has been studied in a triple quadrupole mass spectrometer. Intensity distributions of the various nickel carbonyl ions are measured. Irradiation with a cw Ar+ laser beam demonstrates that efficient detachment of CO ligands occurs following single photon absorption by the metal cluster core. Laser-induced photodesorption is used to counterbalance the adsorption processes, in order to control the molecular coverage of the metal cluster. Time-resolved measurements of the kinetics of these two competing processes have been performed. A rate equation model is proposed which brings a detailed understanding of the kinetics and allows derivation of numerical values for the chemisorption rate constant and for the photoabsorption cross section.