Ultraviolet photoelectron spectra of three Tm@C82 isomers

Ultraviolet photoelectron spectra (UPS) of three Tm@C82 isomers were measured with a synchrotron radiation light source. The upper valence band spectra (0-5 eV) of three isomers are different each other and they also differ from those of other trivalent metal atoms encapsulated metallofullerenes, such as La@C82, Sc@C82 and Gd@C82. Resemblance of the spectra of Tm@C82 (II) and Ca@C82 (III) suggests identical cage structures of these two metallofullerenes. The UPS are well reproduced by simulated spectra obtained with ab initio calculation, which indicates that isomers I-III have Cs (No. 4), C2 (No. 5) and C2v (No. 9) cage structures.