Charge transfer from potassium into the t1g band of C60

Depositing C60 on potassium multilayers creates a K-rich environment for low coverages of C60 and photoemission spectra show that not only the t1u but also the t1g band is occupied. This is direct evidence for the formation of KxC60 with 6<x<12, which could not be achieved in previous studies where K was evaporated onto solid C60 surfaces. However, less than one electron can be transferred to C60 from submonolayer coverages of K on Rh(111) and hence even the t1u band is mostly unoccupied, despite the large K-induced drop in work function from 5.4 to 1.8 eV.