Photoabsorption spectra of Ti8C12 metallocarbohedrynes: Theoretical spectroscopy within time-dependent density functional theory.

The photoabsorption spectra of several of the most stable isomers of the Ti8C12 metallocarbohedryne are calculated using time-dependent density functional theory. Several ground-state magnitudes have been also calculated, such as cohesive energies, electronic gaps between the highest occupied and lowest unoccupied molecular orbitals, and static polarizabilities. Since significant differences are found among the photoabsorption spectra of the different isomers in the low energy region (0-5 eV), we propose the comparison of experimental and the calculated absorption spectra as a tool to elucidate the isomers that appear to form in the experiments. Between 10 and 13 eV all the spectra show a region of high absorption that we identify as due to collective electronic excitations. The existence of this prominent feature explains the occurrence of delayed ionization and delayed ion emission phenomena observed in previous experiments.