IR, NIR, and UV Absorption Spectroscopy of C₆₀²⁺ and C₆₀³⁺ in Neon Matrixes

C₆₀²⁺ and C₆₀³⁺ were produced by electron-impact ionization of sublimed C₆₀ and charge-state-selectively codeposited onto a gold mirror substrate held at 5 K together with neon matrix gas containing a few percent of the electron scavengers CO₂ or CCl₄. This procedure limits charge-changing of the incident fullerene projectiles during matrix isolation. IR, NIR, and UV–vis spectra were then measured. Ten IR absorptions of C₆₀²⁺ were identified. C₆₀³⁺ was observed to absorb in the NIR region close to the known vibronic bands of C₆₀⁺. UV spectra of C₆₀, C₆₀⁺, and C₆₀²⁺ were almost indistinguishable, consistent with a plasmon-like nature of their UV absorptions. The measurements were supported by DFT and TDDFT calculations, revealing that C₆₀²⁺ has a singlet D_5d ground state whereas C₆₀³⁺ forms a doublet of C_i symmetry. The new results may be of interest regarding the presence of C₆₀²⁺ and C₆₀³⁺ in space.