Negative-ion photoelectron spectroscopy has been applied in order to obtain size dependent information
about the electronic structure of clusters of metal atoms solvated with polar molecules. In the present
paper we have investigated the photoelectron spectra of Cu2-(H2O)n, cluster ions with 2 = 0–4 and also
those of Cu2-(H2O)n, with n = 0 and 1. In the spectra of Cu2-(H2O)n, the lowest energy bands were assigned
to the electron detachment from the CuOH-(H2O)n−1, which were produced in the source together with
the above cluster ions. The observed bands for Cu2-(H2O)n were all assigned to the transitions to the
states originating in the ground 2S and first excited 2D states of the Cu atom. The stepwise hydration for Cu- and Cu2- was discussed from the observed spectral shifts.
