An experimental and theoretical description of the (NH3)n−1{NH3–H–H2O}+ cluster ions produced by fast ion bombardment

The (NH3)n−1{NH3–H–H2O}+ cluster series produced by 252Cf fission fragments (FF) impact onto a NH3–H2O ice target have been analyzed theoretically and experimentally. The ion desorption yields show a smooth dependence of the cluster population on its mass, with a relative higher abundance for n = 3. Results of DFT calculations show that two main series of cluster ions may be formed corresponding to the {H3O}+ and {NH4H2O}+ cores. The theoretical analysis shows that the members of the (NH3)n−1{NH4–H2O}+ series are more stable than those of the (NH3)n{H3O}+ series, the (NH3)2{NH3–H–H2O}+ structure being the most stable one, in agreement with the experiments.