Ultrafast Dynamics of Electron Localization and Solvation in Ice Layers on Cu(111)

The femtosecond dynamics of localization and solvation of photoinjected electrons in ultrathin layers of amorphous solid ${\mathrm{H}}_{\mathrm{2}}\mathrm{O}$ and ${\mathrm{D}}_{\mathrm{2}}\mathrm{O}$ have been studied by time- and angle-resolved two-photon-photoelectron spectroscopy. After electron transfer from the metal substrate into the conduction band of ice, the excess electron localizes within the first 100 fs in a state at 2.9 eV above $E_F$, which is further stabilized by 300 meV on a time scale of 0.5–1 ps due to molecular rearrangements in the adlayer. A pronounced change of the solvation dynamics at a coverage of $\sim 2$ bilayers is attributed to different rigidity of the solvation shell in the bulk and near the surface of ice.