The　ground-state　electronic/geometrical　structures　of　the　three　classical　isomers　Cs(15)-C84,　C2(13)-C84,　and　C2(8)-C84　as　well　as　the　corresponding　embedded　derivatives　U@Cs(15)-C84,　YCN@C2(13)-C84,　and　U@C2(8)-C84　have　been　calculated　at　the　density　functional　theory　(DFT)　level.　Then,　the　isomers　of　C84　were　theoretically　identified　by　X-ray　photoelectron　spectroscopy　(XPS)　and　near　X-ray　absorption　fine-structure　spectroscopy　(NEXAFS).　The　spectral　components　of　total　spectra　for　carbon　atoms　in　various　local　environments　have　been　investigated.　The　ultraviolet-visible　(UV-vis)　absorption　spectroscopies　of　U@Cs(15)-C84,　YCN@C2(13)-C84,　and　U@C2(8)-C84　have　also　been　performed　utilizing　time-dependent　(TD)　DFT　calculations.　The　UV-vis　spectra　are　in　good　agreement　with　the　experimental　results.　These　spectra　provide　an　effective　method　for　the　identification　of　isomers.　The　results　of　this　study　can　offer　useful　data　for　further　experimental　and　theoretical　studies　using　X-ray　and　UV-vis　spectroscopy　methods　on　freshly　synthesized　fullerene　isomers　and　their　derivatives.　©　2023　American　Chemical　Society.