Lateral hopping of CO on Cu(111) induced by femtosecond laser pulses

We present a theoretical study of the lateral hopping of a single CO molecule on Cu (111) induced by femtosecond laser pulses by Mehlhorn et al. [Phys. Rev. Lett. 104, 076101 (2010)]. Our model assumes an intermode coupling between the CO frustrated translation (FT) and frustrated rotation (FR) modes with a weak and strong electronic friction coupling to hot electrons, respectively, and heat transfer between the FT mode and the substrate phonons. In this model the effective electronic friction coupling of the FT mode depends on the absorbed laser fluence F through the temperature of the FR mode. The calculated hopping yield as a function of F nicely reproduces the nonlinear increase observed above F=4.0 J/m(2). It is found that the electronic heating via friction coupling nor the phonon coupling alone cannot explain the experimental result. Both heatings are cooperatively responsible for CO hopping on Cu (111). The electronic heat transfer dominates over the phononic one at high F, where the effective electronic friction coupling becomes larger than the phononic coupling