XAFS studies of the oxidation process in Rb xCs yC 60 ( x=3, y=0 and x=2, y=1)

Abstract

EXAFS measurements of the alkali-doped fullerence superconductors, Rb x Cs y C 60 ( x=3, y=0 and x=2, y=1 with T c=30 and 31 K, respectively), have been made at the Rb K-edge as a function of exposure time to O 2 gas. The distances r Rb-C=3.35±0.02 and 3.31±0.02 Å were obtained for pristine Rb x Cs y C 60 of x=3, y=0 and x=2, y=1, respectively, in good agreement with the reported value of 3.33 Å at the tetrahedral site determined by X-ray diffraction study. The analysis of the Rb-O EXAFS in Rb 3C 60 exposed to O 2 for 40 h gives r Rb-O=2.89±0.05 Å and N=4±1, consistent with the crystallographic values of rubidium oxide (Rb 2O: r Rb-O=2.91 Å and N=4 at room temperature). The result indicates that the Rb in Rb x Cs y C 60 is converted into Rb 2O through the oxidation.