AVS 53rd International Symposium
    Surface Science Monday Sessions
       Session SS2-MoM

Paper SS2-MoM1
Biphasic Substrate-Adsorbate Energy Transfer Following Subpicosecond Photoexcitation

Monday, November 13, 2006, 8:00 am, Room 2004

Session: Gas-Surface Reaction Dynamics
Presenter: N. Camillone III, Brookhaven National Laboratory
Authors: P. Szymanski, Brookhaven National Laboratory
A.L. Harris, Brookhaven National Laboratory
M.G. White, Brookhaven National Laboratory
N. Camillone III, Brookhaven National Laboratory
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Photodesorption of carbon monoxide molecules from a Pd(111) surface caused by femtosecond laser pulses was studied by two-pulse correlation measurements. The measured decay of the desorption yield with pump-probe delay reveals that the dynamics of energy transfer are independent of surface coverage and are biphasic, comprising two components with subpicosecond and 30-ps characteristic decay times. The relative contribution of the slower component to the total desorption yield is found to decrease as the difference between the desorption temperature and the surface temperature increases. This behavior is consistent with simultaneous excitation coupling from both electrons and phonons of the metal into the adsorbate-substrate bond. The strong contributions from two separate coupling mechanisms is distinct from that observed for CO desorption from other metals (e.g., Cu and Ru), where either fast or slow coupling predominates.