Abstract

Femtosecond optical excitation of surfaces creates a unique environment for molecular adsorbates that can initiate surface chemistry. Of particular importance to femtosecond photoprocesses on metal surfaces are the energy-transfer mechanisms in highly perturbed hot adsorbate/substrate systems. Several experiments have used intense femtosecond excitation of the substrate to desorb diatomic molecules from metal surfaces.¹·² Complementary experiments of energy-transfer rates with low-power excitation pulses have also been performed.³-⁴ However, when molecules are excited near the desorption threshold, anharmonic couplings between different adsorbate modes and altered electronic potentials will effect energy-transfer processes. Coupling rates measured at low excitation therefore may not be valid in the desorption regime.

© 1995 Optical Society of America