Catalytic Oadsorbed + Oadsorbed = O2,gas desorption from c(2X2)-O and p(5X5)-O phases on single crystal Pd(1 0 0) surface: Observing the unseen using femtosecond laser spectroscopy

Abstract

Conventional thermal activation-based methods (such as temperature programmed desorption measurements) can monitor recombinative Oadsorbed + Oadsorbed = O2,gas desorption only from the (√5X√5)R27O-O and p(2x2)-O phases on the single crystal Pd(100) surface. Both the c(2X2)-O and p(5X5)-O phases remain silent in this overall thermally activated recombinative desorption process. With the help of femtosecond laser excitation, for the first time, we demonstrate that both c(2X2)-O and p(5X5)-O phases can be made active for the recombinative Oadsorbed + Oadsorbed = O2,gas desorption. Thus, femtosecond laser excitation opens door to the investigation of the surface chemical reactions which otherwise cannot be probed with the help of conventional thermal heating process. Finally, ultrafast dynamics of the recombinative Oadsorbed + Oadsorbed = O2,gas desorption from the c(2X2)-O and p(5X5)-O phases is presented.