Identifying isomers of ${\mathrm{C}}_{78}$ by means of x-ray spectroscopy

X-ray photoelectron and absorption spectra of ${\mathrm{C}}_{78}$ isomers have been generated using density functional theory with inclusion of the full core-hole potentials. Strong isomer dependence has been found in absorption, but not in the photoelectron spectra. ${\mathrm{C}}_{78}$ isomers can be thought to be formed by inserting 18 carbon atoms into an opened ${\mathrm{C}}_{60}.$ We have shown how the different local arrangements of these 18 carbon atoms are responsible for the significant isomer dependence observed. Our calculated spectra are in excellent agreement with the experimental counterparts.