Multiple CO Bonding States on Potassium-Dosed Cu(100).

Vibrational spectra for carbon monoxide chemisorbed on potassium predosed Cu(100) were examined at a variety of K precoverages and CO doses. At least seven different vibrational states of CO have been found ranging in frequency from 1220 [EQ]cm sup -1[EN] to 2090 [EQ]cm sup -1[EN] with as many as five states coexisting on a single surface. Based upon the ranges of K coverage required for the existence of each state, a model is suggested where the CO is influenced by (1) 2[EQ]pi sup *[EN] backbonding, (2) bond site changing and/or (3) short- range K interactions, in varying degrees, depending upon the state.