Ultrafast electron solvation dynamics in D2O/Cu(1 1 1): influence of coverage and structure

Using femtosecond time-resolved two-photon photoelectron spectroscopy we have studied the dynamics of photoexcited electrons injected from a Cu(1 1 1) substrate into the conduction band of ultrathin ice layers. Ultrafast localization of the injected electrons within <50 fs is followed by a stabilization on a time scale of 0.1–1 ps due to local rearrangements of water dipoles. The dynamics of this electron solvation process are very similar for amorphous and crystalline ice, but exhibit a pronounced coverage dependence with two different regimes, which are attributed to solvation sites in the interior and at the surface of the adlayer. Additional information on the adsorbate structure is obtained from low-temperature scanning tunneling microscopy.