Electron-energy-loss Spectroscopy of KxC60 and K-halides: Comparison in the K3p excitation region

We have investigated the electronic structure of KxC60 (x = 0 ~ 6) using low-energy electron energy loss spectroscopy (LEELS), especially focusing on the K3p core-electron excitation spectra. It is found that the structure of the K3p-excitation spectrum of KxC60 quite differs from that of KCl. Furthermore, the K3p-excitation LEELS of K3C60 has been revealed to be different from that of K6C60. K3p electrons are excited into K4sand K3d-derived empty states in both KxC60 and KCl, but in the case of KxC60 the K3d-derived empty states have a rather complicated structure where several levels are not well separated. Consequently K3p-excitation LEEL spectra of KxC60 show wide-spread plateau-like structures. The difference in the K3p-excitation spectra of K3C60 and K6C60 is considered to originate from the different crystal field around K cations in the C60 molecular crystal.