Formation of large water clusters by IR laser resonant desorption of ice

Large H3O+(H2O)n clusters, up to n ≈ 100, were produced by IR laser resonant desorption of an ice matrix using an optical parametric oscillator (OPO) at 3.1 μm. 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.