Bulk electronic structure of K3 C60 as revealed by soft x-rays

We present C 1s x-ray absorption, x-ray emission, and resonant inelastic x-ray scattering (RIXS) spectra of single-phase crystalline K3 C60. The comparison to valence-band photoelectron spectra from the same sample facilitates identification of the contribution from surface and bulk electronic states in the latter. Bulk-sensitive techniques show that the valence bands of K3 C60 and pure C60 are characterized by spectral features of similar width, in agreement with the predictions of band-structure calculations. Symmetry selectivity in the RIXS process allows us to assign peaks in the C 1s absorption spectrum, demonstrating a close correspondence with pure C60 also in the conduction band. The symmetry selectivity is as pronounced in K3 C60 as in pure C60, indicating that the local C60 symmetry is not appreciably affected by the K doping, either in the ground state or intermediate state, on the time scale of 6 fs.