G. Lüttgens, N. Pontius, P.S. Bechthold, M. Neeb, and W.Eberhardt

The dissociation of the cluster-adsorbate-systems Pt2(CO)5- and AU2CO-have been recorded by measuring femtosecond-time-resolved 2-photon-hotoelectron-spectra. Both clusters loose one CO-molecule after absorption of a 1.5e V-pump-photon. While the dissociation of AU2CO- seems to occur via a dissociative state within some hundred fs after excitation, Pt2(CO)5-evaporates CO in a statistical manner after thermalization of the absorbed energy. An ultrafast electronic relaxation process of the photo-excited state can in addition be seen in the spectra at low binding energies.