Stabilities and dissociation reactions of the Irm(CO)n+ ions observed in TOF-SIMS of Ir4(CO)12 thin layer

► We measured the kinetic energy of ion by DPA method without reducing mass resolution. ► Apparent mass shift and kinetic energy of Irm(CO)n+ show clear correlation. ► The kinetic energy of Irm(CO)n+ depends on the number of CO but not on that of Ir. ► The signal of Ir5(CO)12+ is absent in the TOF-SIMS of Ir4(CO)12 layer. ► Structure change of Ir5+ shell is induced by the coordination of CO (at Ir5(CO)12+).