133Cs NMR in C 60 superconductors: CsxRb3− xC60( x=1,2)

Abstract

133Cs NMR study in superconductors Cs xRb 3-xC 60 (x=1,2) above 77K is reported. For x=1, single absorption line was observed at −370±15 ppm with respect to that of CsCl aqueous solution at 300K, while for x=2 two lines at −120±25 ppm and −380±20 ppm were observed. The signal around −370 (−380) ppm was assigned to the Cs atoms intercalated in octahedral sites of fcc lattice in both of x=1 and 2, and the other line at −120ppm in x=2 to tetrahedral sites. These line positions (Knight shift) are close to that for second stage Cs-graphite intercalation compound, and are far from +1.48% of Knight shift in Cs-metal, indicating a negligible electronic density of state at the Fermi-level in the Cs sites.