Theoretical Identification of the Smallest Fullerene, $C_{20}$

By using first-principles calculations, we calculate the vibronic fine structure in photoelectron spectra of ${\mathrm{C}}_{20}^{-}$ clusters. Based on our results, we assign one of the recently observed spectra [H. Prinzbach et al., Nature (London) 407, 60 (2000)] to the fullerene structure and, therefore, confirm the experimental claim that the smallest fullerene is really synthesized.