a) Adapted from Fig. 5 of Pennington & Stenger (1996). Schematic diagram of basic electronic shells of C₆₀ in Hückel approximation and resulting first excited states of C₆₀ (E< ~ 3 eV), singlet (see e.g. Sassara et al. 1997, 2001) and triplet. b) From Table 6 of Bendale et al. (1992). Schematic diagram of the first electronic levels of C connected to the ground state with a computed oscillator strength f ≥ 0.003. Both the I_h parent geometry of C₆₀ and the D_5d geometry found for C are reported. The levels of the C 9577/9633 Å DIBs are shown in red (the H_g E_1g excited level corresponds to the promotion of one electron of the h_g HOMO-1 shell of C₆₀ to the h_u HOMO shell).