Large H3O+(H2O)(n) clusters, up to n n approximate to 100, were produced by IR laser resonant desorption of an ice matrix using an optical parametric oscillator (OPO) at 3.1 mu m. The velocity distribution has been analyzed to characterize the laser-sample interaction and the plume dynamics desorption. The velocity distribution curves of the clusters show two distinct components corresponding to a phase explosion regime followed by vaporization. We discuss the shift of these curves with mass and the formation mechanism. A distinction in the desorption process is made between small and large clusters. (c) 2005 Elsevier B.V. All rights reserved.