Photoelectron spectroscopy of (CO2)(n)(-) revisited: Core switching in the 2<=n<=16 range

Photoelectron spectra of (CO2)(n)(-) have been measured at a photon energy of 4.66 eV, and the vertical detachment energy (VDE) determined as a function of the cluster size, 2 less than or equal to n less than or equal to 16. The n-dependence of the VDE shows sharp discontinuities between n = 6 and 7, and between n = 13 and 14, indicating that CO2- and C2O4- are formed as the core anions in (CO2)(7)(-) and (CO2)(14)(-), respectively. From these findings we infer that the anionic core of (CO2)(n)(-) changes promptly from CO2- to C2O4- and vice versa when 'core switching' results from the formation of geometrically favored structures.