The absorption and fluorescence spectra of silver trimers isolated in an Ar matrix show the existence of three distinct lattice sites whereby the population of each site depends on the conditions of matrix preparation. Irradiation of certain absorption bands of the trimer isolated in one of these sites results in an irreversible reorganization of the matrix surrounding and population of another site. The experiments were performed with matrices prepared either by the matrix isolation/aggregation method or by soft landing of size-selected Ag-3 species.