Electronic structure of KxC60− in the gas phase

Abstract
The photoelectron spectra of KxC60 (x=1–3) have been studied in the gas phase, and the electron affinities obtained. These were found to decrease linearly with the number of K atoms. The result is consistent with an ionic description of the K–C60 chemical bonding, with each K atom donating its outer 4s electron to the t1u orbital of C60. Vibrational autodetachment from a weakly bound excited electronic state was discovered in KC60, and a series of three equally spaced peaks were assigned to a progression in the intermolecular K–C60 stretching vibration with a frequency of 140 cm−1.