Electronic states and phases of K(x)C60 from photoemission and X-ray absorption spectroscopy

High-resolution photoemission and soft X-ray absorption spectroscopic techniques are presently applied to K(x)C60, which has been found to be superconductive below 19.3 K at x values of about 3. The observations obtained indicate that the conduction band formed from the lowest unoccupied molecular orbital of C60 is of C 2p character; the nonrigid-band shift, together with the anomalous occupied bandwidth, implies that there is significant mixing between the electronic states of K and C60 in the superconducting phase.