Dissolution of sodium trimer in water clusters is studied by photoelectron and photodissociation spectroscopies of Na-3(-)(H2O)(n). The photoelectron spectrum is found to exhibit transitions from the anion to the neutral ground and first excited states merge into each other with increasing n. The huge spectral change is ascribed to the dissolution of Na-3(-) core into Na-2(-) and Na based on ab initio calculations for the structures and energies of these clusters. The theoretical prediction is confirmed with the photodissociation experiments of Na-3(-)(H2O)(3). On the basis of these results, we discuss the stepwise dissolution of metal aggregates in water clusters. (c) 2005 Elsevier B.V. All rights reserved.