The electronic properties of the metal atoms encaged in a fullerence cage were investigated using synchrotron X-ray photoelectron
spectroscopy. Systematic variations in photoemission of valence band of Gd@C82, Gd@C82(OH)12, and Gd@C82(OH)22 were observed in Gd 5p levels. The results suggest that the electronic properties of the inner metal atom can be efficiently
modulated by surface chemistry of the fullerene cage.