A dynamic landscape from femtoseconds to minutes for excess electrons at ice - metal interfaces

Stabilization of excess electrons is studied at crystalline ice-metal interfaces by femtosecond time-resolved two-photon photoelectron spectroscopy and ab initio calculations. Following optical excitation into delocalized image potential states, electrons localize at pre-existing defects which are located at the ice-vacuum interface. Remarkably, the stabilization of these trapped electrons is monitored continuously from femtoseconds up to minutes. By first principle calculations we identify defect structures, that support excess electrons in front of crystalline ice surfaces, and suggest that the stabilization proceeds through subsequent conformational substates. The excess electron wave functions are efficiently screened from the underlying bulk and explain the long residence times observed in the experiment. Thereby, we shed light on the collective character of the nuclear rearrangement that determines the energetics over all timescales.