Highly efficient ultrafast energy transfer into molecules at surface step sites

Ultrafast laser-induced desorption of NO and CO molecules on a platinum surface reveals that the rate of energy transfer between the laser-heated electrons and the adsorbate depends critically on the precise adsorbate location. An analysis based on a simple electronic friction model suggests that this femtosecond energy transfer occurs ~3 times faster to adsorbates at step sites compared to adsorbates located on atomically flat surface regions. Density functional theory calculations of vibrational damping rates by electron-hole pair excitations corroborate the increased rate of energy transfer at step sites and show that it is caused primarily by an increased local density of adsorbate-induced states around the Fermi level.