Microscopic solvation process of single Li atom in small water clusters

We examine the photoelectron spectra of negatively-charged water clusters containing a Li atom, Li−(H2O)n (n⩽10), to reveal the hydration state of the Li atom in water clusters. The 2S- and 2P-type transitions of Li are found to be shifted to the lower electron binding energy with increasing cluster size up to n=4 and then shift back to higher binding energy for n⩾5. We discuss these results in relation to the spontaneous ionization of the Li atom and the formation of two-center ion-pair state, which is a counter part of hydrated electron.