AVS 49th International Symposium
    Surface Science Tuesday Sessions
       Session SS1-TuA

Paper SS1-TuA3
Observation of Isotope Effect in Femtosecond Laser-Induced Desorption of O@sub 2@/Pd(111)

Tuesday, November 5, 2002, 2:40 pm, Room C-108

Session: Ultrafast Phenomena & Dynamics at Surfaces
Presenter: D.P. Quinn, Columbia University
Authors: D.P. Quinn, Columbia University
T.F. Heinz, Columbia University
Correspondent: Click to Email
A significantly higher yield for femtosecond laser-induced desorption is observed for @super 16@O@sub 2@ than for @super 18@O@sub 2@ in the saturated co-adsorbed @super 16@O@sub 2@ + @super 18@O@sub 2@/Pd(111) system. Similar isotope effects@footnote 1@ have been reported for conventional photochemistry and electron-stimulated desorption. Such isotope effects have also been used to examine reaction mechanisms for femtosecond laser-induced surface processes.@footnote 2,3@ In the present case, investigations of the O@sub 2@/Pd(111) system have demonstrated that the desorption process is mediated by the substrate electronic excitations induced by the femtosecond laser pulses. The observation of a significant isotope effect is compatible with such an electronic mechanism, but implies that the adsorbed molecules are out of equilibrium with the electronic degree of freedom of the substrate during the desorption process. We consider this phenomenon in the context of both DIMET@footnote 4@ and electronic friction models of the adsorbate-substrate coupling. @FootnoteText@ @footnote 1@ T.E. Madey et al., J. Chem. Phys. 52, 5215 (1970). @footnote 2@ R.J. Finley et al., Chem. Phys. Lett. 274, 499 (1997). @footnote 3@ M. Bonn et al., Science 285, 1042 (1999).@footnote 4@ J.A. Misewich et al., Phys. Rev. Lett. 68, 3737 (1992).