X-ray　photoelectron　(XPS)　and　near-edge　X-ray　absorption　fine　structure　(NEXAFS)　spectra　as　well　as　the　ground-state　electronic/geometrical　structures　of　#540C54　captured　in　experiment　and　the　most　controversial　isomer　#369C54　(C2v-　and　Cs-symmetry,　respectively)　have　been　calculated　at　the　density　functional　theory　(DFT)　level.　After　chlorination,　significant　changes　were　observed　in　the　electronic　structure　and　X-ray　spectra.　Both　XPS　and　NEXAFS　spectra　showed　strong　isomer　dependence.　The　results　indicated　that　the　＇fingerprints＇　in　the　X-ray　spectra　afforded　an　effective　way　to　identify　the　fullerene　isomers　mentioned　above.　Ultraviolet-visible　(UV-Vis)　absorption　spectroscopy　of　C54Cl8　was　also　simulated　at　the　time-dependent　(TD)　DFT　level,　and　the　simulated　UV-Vis　spectrum　was　in　accordance　with　the　experimental　result.　The　results　of　this　study　can　provide　valuable　information　for　further　experimental　and　theoretical　studies　of　new　fullerenes　and　their　derivatives　through　X-ray　and　ultraviolet　spectroscopy.　The　study　of　newly　synthesized　fullerene　isomers　and　their　derivatives　using　X-ray　and　UV-Vis　spectra　offers　valuable　information　for　further　experimental　and　theoretical　exploration.　©　The　Royal　Society　of　Chemistry　2017.