Odd-numbered carbon-only anion clusters, C53-, C55-, C57-, and C59-, a
re observed in laser desorption ionization of C60O obtained in reactio
ns of C60 with O3. These odd-numbered carbon clusters are suggestive o
f the presence of the ether form monoxide resulting from oxygen insert
ion into the C-C bond shared by adjacent five- and six-membered rings.