Surface femtochemistry of 02 and CO on Pt(111)

Desorption of OZ and formation of CO2 were induced with subpicosecond laser pulses on a Pt(111) surface dosed with coadsorbed OZ and CO. We report the fluence dependent yields obtained over a range of laser wavelengths from 267 to 800 nm, and pulse durations from 80 fs to 3.6 ps. The nonlinear dependence of the yield on fluence is different at different wavelengths. Two-pulse correlation measurements show two different time-scales relevant to the desorption. The results show that nonthermalized electrons play a role in the surface chemistry, and that an equilibrated pre-heating of the surface modes leads to enhanced desorption.