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要旨

Structural information for neutral magnesium oxide clusters has been obtained by a comparison of their experimental vibrational spectra with predictions from theory. (MgO)_n clusters with n = 3–16 have been studied in the gas phase with a tunable IR-UV two-color ionization scheme and size-selective infrared spectra have been measured. These IR spectra are compared to the calculated spectra of the global minimum structures predicted by a hybrid ab initio genetic algorithm. The comparison shows clear evidence that clusters of the composition (MgO)_3k (k = 1–5) form hexagonal tubes, which confirm previous theoretical predictions. For the intermediate sizes
(n ≠ 3k) cage-like structures containing hexagonal (MgO)₃ rings are identified. Except for the cubic (MgO)₄ no evidence for bulk like structures is found.