Decay dynamics of photoexcited alkali chemisorbates: Real-time investigations in the femtosecond regime

Abstract
The inelastic decay time of photoexcited cesium and sodium adsorbed on different single-crystal surfaces has been investigated by means of time-resolved two-photon photoemission. Especially in the case of cesium, we observe a surprisingly high lifetime. For Cs/Cu(111) we obtain a value of 15±6fs. Intra-atomic hybridization, the specific band structure of the substrate, and adsorption site effects may be responsible for this behavior. These different mechanisms are discussed in detail.