Photoelectron spectra of thulium atoms encapsulated C82 fullerene, Tm2@C82 (III) and Tm2C2@C82 (III)

Ultraviolet photoelectron spectra (UPS) and X-ray photoelectron spectra (XPS) of two thulium atoms and thulium-carbide cluster entrapped fullerenes, Tm-2@C-82 (III) and Tm2C2@C-82 (III), were measured using synchrotron radiation and MgK alpha X-ray light sources. The UPS spectral onset energy of these endohedral fullerenes is around 0.9 eV, which is smaller than that of 1.2 eV of empty C-82. The UPS of Tm-2@C-82 (III) and Tm2C2@C-82 (III) resemble each other. Further, the UPS of Tm-2@C-82 (III), Y-2@C-82-C(3)v and Er-2@C-82-C-3v are almost identical and as well as are Tm2C2@C-82 (III), Y2C2@C-82-C-3v and Er2C2@C-82-C(3)v. The XPS Tm(4)d(5/2) peaks of Tm-2@C-82 and Tm2C2@C-82 appear at higher binding energy region than that of Tm@C-82, which suggests the oxidation states of Tm atoms in Tm-2@C-82 (III) and Tm2C2@C-82 are higher than that in Tm@C-82. (C) 2014 Elsevier B.V. All rights reserved.