Ultrafast electron solvation at the room temperature ionic liquid/metal interface

Abstract

Ultrafast electron solvation was studied in thin films of the room temperature ionic liquid [Bmpyr]+ [NTf2]- on a Ag(111) substrate. Two-photon photoemission spectra reveal a solvation effect which increases from a 250 meV shift in under 400 fs for the monolayer to a 1 eV shift in over 100 ps for the trilayer. The state’s binding energy relaxes along the same path for all coverages at a given temperature, suggesting that the solvation process is insensitive to film thickness. Time-dependent population analysis showed that the lifetime of solvation changes with coverage due to charge screening. In the monolayer coverage regime, the state has dispersive, delocalized character at early times and nondispersive, localized character after 200 fs.