  Positively charged zinc oxide clusters ZnnOm (up to n = 16, m <= n) of
various stoichiometry were synthesized in the gas phase by excimer ArF laser
ablation of a ZnO target and investigated using time-of-flight mass
spectrometry. Depending on ablation conditions, either metal rich or
stoichiometric clusters dominate in the mass spectrum. When the irradiated
target surface is fairly fresh, the most abundant clusters are metal rich with
Zn(n+1)On and Zn(n+3)On being the major series. The stoichiometric clusters are
observed with an etched ablated surface. The magic numbers at n = 9, 11 and 15
in mass spectra of (ZnO)n clusters indicate that the clusters have hollow
spheroid structures related to fullerenes. A local abundance minimum at n = 13
provides an additional evidence for the presence in the ablation plume of
fullerene-like (ZnO)n clusters.
