Ionic fragmentation following the inner-shell photoexcitation of [(CH3)(2)CO]Ar-n heteroclusters was investigated in the Ar L-23- and O K-edge regions. A partial ion yield (PIY) measurement revealed that Ar-n(+) and various acetone fragments (H-m(+), CHm+, C2Hm+, C3Hm+, and CHmCO+) were produced following the Ar L23- shell excitation. In the O K-edge region, the PIY of O+ exhibited a sharp resonance peak at the O 1s -> pi*(C=O) resonance excitation. The selective O+ formation was interpreted as the suppression of statistical fragmentation, which was dominant in isolated acetone, owing to the dissipation of excess energy into Ar clusters. (C) 2008 Elsevier B.V. All rights reserved.