Structural Characterization of Unprecedented Al14O– and Al15O2–: Photoelectron Spectroscopy and Density Functional Calculations

New aluminum oxide clusters Al 14 O – and Al 15 O 2 – were observed unprecedentedly in the gas-phase reaction of Al n – and O 2 . Photoelectron spectroscopic measurements and density functional calculations indicated that Al 14 O – and Al 15 O 2 – are composed of an icosahedral Al 13 moiety bonded by one and two OAl unit(s), respectively. The preferential formation of Al 14 O – and Al 15 O 2 – is explained in terms of the high stability associated with the Al 13 moiety and efficient collisional trapping as intermediates of oxidative etching reactions.