We have studied electron stimulated desorption (ESD) and photon stimulated desorption (PSD) of positive ions from water absorbed on a surface of solid rare gases. In TOF spectrum, a series of ionized clusters are observed, which were thought to be protonated water clusters, (H2O) nH+. In both PSD experiments of H2O/Ar, the desorption threshold of (H2O) nH+ was found to be coincide to 2p core ionization of Ar.
