Gd–LIII EXAFS study of structural and dynamic properties of Gd@C82 between 10 and 300 K

Abstract The location of endohedral Gd ions in Gd@C 82 is studied by Gd–L III X-ray absorption spectroscopy in the temperature range 10–300 K. The near-edge data point to a covalent bond of trivalent Gd ions with the carbon cage. The EXAFS data can be well fitted with a Gd position above a carbon hexagon with two neighbour shells of carbon at distances R 1,2 =2.49(3) and 2.95(5) A, corresponding to a large off-center position of about 1.8 A from the center of the C 82 cage. The second cumulants of these distances are relatively large and weakly depending on temperature. This points to a considerable distribution in Gd–C 1 and Gd–C 2 distances and confirms the relatively strong binding of the Gd ion to the C 82 cage. These results will be discussed together with previous EXAFS studies and theoretical calculations of Y@C 82 and La@C 82 .