Photoionization and photodissociation studies on aluminum-water clusters and their ions

Clusters of aluminum atoms solvated with water molecules, Al(H₂O)_n, have been studied by one-photon ionization and time-of-flight mass spectroscopy. Characteristic feature is observed in the photoionization mass spectrum: The intensities of the product Al⁺(H₂O)_n ions are about one order of magnitude larger for n≤4 than for n≥5. The ionization potentials are determined for n up to 4. The obtained results are discussed in connection with the recent theoretical works. The photodissociation spectroscopy has also been applied to the Al⁺(H₂O)_n ions with n=1-10. The observed spectra are ascribed to the transition localized on the Al⁺ ion on the analogy of the results of Mg⁺(H₂O)_n photodissociation. The dissociation dynamics is also discussed from the fragmentation pattern with the aid of the recent theoretical work on the structure and stability of these ions.