The cavity size of an internal X-(H2O)(n) Cluster is shown, via ab initio calculations, to determine how its charge-transfer-to-solvent precursor excited electron is distributed around the cavity. Thus, we find an optimal cavity size (OCS), at which the excited electron has a maximal vertical binding energy. We argue that the OCS is a consequence of the balance of the electron probability influx into the cavity and the interactions of the excited electron with the parent core and solvent molecules. The implications of these findings to the initial solvent response upon photo-excitation of an anion in liquids are also discussed. (C) 2004 Elsevier B.V. All rights reserved.