Unfilled orbitals of C₆₀ and C₇₀ from carbon K-shell X-ray absorption fine structure

The K-shell near-edge X-ray absorption fine structure spectra of solid C60 and C70 have been recorded with high spectral resolution. The spectra exhibit sharp resonances associated with transitions to unfilled π* molecular orbitals and, at higher energy, broader resonances associated with σ*-like orbitals. The observed energy splitting of the π* resonances can be accounted for by published extended Hückel calculations. Our data clearly reveal that the fullerence films resemble molecular solids with considerably stronger intra-molecular than inter-molecular interactions. © 1991.