Infrared spectroscopy of protonated water clusters: The effects of argon tagging and deuteration

INOR 1082

Michael A Duncan, Department of Chemistry, University of Georgia, Athens, GA 30602-2556
Protonated water clusters, H+(H2O)n are produced by pulsed laser discharge in a supersonic expansion of helium, neon or argon seeded with water. The resulting ions are mass-analyzed and size-selected in a reflectron time-of-flight mass spectrometer. Infrared photodissociation spectroscopy of the size-selected cations probes the O-H stretching and the hydrogen bonding regions of the spectrum, elucidating the isomers formed under different conditions. Tagging with argon produces colder clusters and fewer isomers. Prediction of the specific isomeric structures observed is only possible when zero-point energies and the free energy at finite temperatures are included in theoretical evaluations. Fully deuterated clusters, D+(D2O)n have been studied with and without argon tagging. Differential zero point energy differences are smaller in these systems, and more isomers are present under the same conditions.