Ultraviolet photoelectron spectra of Er _2@C _(82) (I), Er _2@C _(82) (III), Er _2C _2@C _(82) (I) and Er _2C _2@C _(82) (III)

摘要

Ultraviolet photoelectron spectra (UPS) and X-ray photoelectron spectra (XPS) of two erbium atoms and an erbium-carbide cluster entrapped fullerenes, Er _2@C _(82) (I), Er _2@C _(82) (III), Er _2C _2@C _(82) (I) and Er _2C _2@C _(82) (III), were measured using a synchrotron radiation light source and MgKα X-ray gun. The spectral onset energy of these endohedral fullerenes is around 0.8-0.9 eV, which is larger than that of Er@C _(82) (I) of 0.4 eV. The UPS of erbium atoms encapsulated endohedral fullerenes having the same C _(82) cage structure were analogous while those of the different cage structure are different. This finding supports an empirical rule that the electronic structure of the endohedral fullerenes is principally governed by the C _(82) cage structure. The XPS Er4d _(5/2) peak of Er _2@C _(82) suggests the oxidation state of (Er ~(3+)) _2 @C826-. The difference spectrum between the UPS of Er _2@C _(82) (III) and Er _2C _2@C _(82) (III) has the same C _(3v) structure reveals two excess electrons on the cage of Er _2@C _(82).