Carbon K-Edge XANES and EXAFS of C60, C70, and K3C60

Abstract

The carbon K-edge absorption spectra of microcrystal-line C60, C70 and potassium-doped K3C60 have been measured using 250 – 500 eV synchrotron radiation. The C60 and C70 fullerenes exhibit π* and σ* resonances as has been observed in the carbon K-edge XANES (X-ray absorption Near-Edge Structure) spectra of graphite. However, the XANES spectra of C60 and C70 show fine structures in both of the resonances, and most of the spectral positions of the observed peaks are in good agreement with a reported density-of-state (DOS) calculation. The XANES feature of K3C60 consists of the carbon K-edge and the potassium L-edge absorption which is overlapped with the a transition of the carbon K-edge absorption. While EXAFS features of pure C60 and C70 are very weak, those of the potassium-doped K3C60 are clearly observable. A Fourier transformation of the extracted EXAFS oscillation with an assumed phase factor gives the nearest-neighbour K-C distance of 3.1 A for K3 C60.