Ion-induced desorption of (H2O)/sub n/H+ ion clusters

The mass distribution of (H2O)/sub n/H+ ion clusters desorbed from ice at 78 K was measured for 1≤n≤40. The desorption was induced by bombardment of the ice by three different primary ions, Ne+, Ar+, and Kr+ at 6 keV. The mass distribution can be described by RRK theory which fits the relative ion yields Y/sub n//Y1, i.e., the ratio of the yield of the nth cluster to that of the first cluster, as a function of n. The energy deposited per normal mode required for desorption caused by each bombarding ion species is calculated from our theoretical fits to the experimental data. This is then compared with the energy deposited per mode estimated from the energy loss due to nuclear stopping of the bombarding ion in the ice. Reasonable agreement between the two is obtained. The existence of the ''magic number'' cluster ion (H2O)4H+ was observed in each of the three bombardment schemes