Energy spectrum and optical absorption of carbon nanosystems: isomers nos. 11 and 22 of C$_{84}$ fullerene

The energy spectra of isomers nos. 11 and 22 of C$_{84}$ fullerene is obtained with allowance for the intrasite Coulomb interaction. Based on the obtained spectra, the optical absorption spectra of these systems are simulated. The obtained optical absorption spectra qualitatively agree well with the available experimental data. In addition, the optical absorption spectra are also calculated on the base of the energy spectra of each of the systems calculated without considering the intrasite Coulomb interaction. The comparison of the results obtained in these different models strongly demonstrates the most important role of the Coulomb interaction in the formation of the electronic and optical properties of these systems.