Electron Attachment to Water Clusters

The attachment of excess electrons to water clusters is studied by computer simulation methods. An efficient Quantum Path Integral Monte Carlo (QPIMC) algorithm for finite temperature molecular systems is used in these studies. The atoms of water clusters are treated classically. The excess electron is represented within the path integral formalism by a cyclic polymer chain. An accurate electron-water pseudo potential and deformable water-water interaction are employed. The bare water dimer system exhibits two important structures which are local minima as function of orientation of the donor molecule. The lowest energy stable geometry has a low dipole moment. The bare dimer also has a metastable structure which has a higher dipole moment. It is found that when the excess electron is attached to the dimer, the molecules reorient to the higher dipole form which favors electron attachment. Vertical electron detachment studies of excess electrons attached to water clusters generated in molecular beams indicate vibrational excitation of the cluster on detachment, which consistent with the findings of structural modification from the simulation. Simulation studies by other workers on the system failed observe structural changes. The studies of the cluster anions with size n = 6 to n = 64 indicate size dependence of both the excess electron localization and electron binding energy. The binding energy shows an n^ {-1/3} dependence. Extrapolating the calculated binding energies to infinite cluster size gives results in agreement with experiments. ftn*All degree requirements completed in 1991, but degree will be granted in 1992.