Temperature Dependence of Local Structure Around Rb+and Cs+Ions in Alkali Doped Fullerenes

Abstract

Rb and Cs K-edge EXAFS spectra have been measured in the temperature range from 10 to 290 K, in order to investigate the temperature dependence of local structure around Rb + and Cs + ions in various alkali doped fullerenes. It has been found that the alkali metal ions in Rb 3 C 60 , K 2 RbC 60 and Na 2 CsC 60 , occupy the center of the tetrahedral and octahedral sites of C 60 crystals. The metal ion in the octahedral site exhibits a large fluctuation in comparison with that in the tetrahedral site. The increase in σ(2) of the t-site Rb-C for Rb 3 C 60 has been observed around T∂ while the increase in σ(2) has not clearly been observed for the o-site Rb-C in K 2 RbC 60 . The local structure around Rb + ion in non-superconducting alkali doped fullerene Rb 6 C 60 has also been studied to compare with that in superconducting fullerenes.