STABILITY AND FRAGMENTATION OF PROTONATED HELIUM DIMERS FROM AB-INITIO CALCULATIONS OF THEIR POTENTIAL-ENERGY SURFACES

Ab initio calculations are carried out on the helium neutral dimer int eracting with a ''foreign'', ionic probe like H+. The most stable stru cture is found to be with the ionic core symmetrically at the center o f the two helium atoms, while a less stable configuration is given by the asymmetric linear system with the ion external to the cluster. The nonlinear, C-2 nu, arrangement is also studied and its fragmentation aspects are examined. The three lowest excited electronic states are a lso presented, and the possible results from cluster excitation and fr om the ensuing fragmentation patterns are discussed in detail in terms of the species that are expected to be formed, like HeH+, He-2(+), an d He+ from charge-transfer excitations. The study should help to bette r understand the breakup dynamics of the larger protonated helium clus ters that are currently of interest to experiments and theory.