High resolution x-ray photoelectron spectroscopy study of Cr(CO) ₆ in the gas phase

The gas phase high resolution x-ray photoelectron spectra of the Cr(CO)₆ metal complex are presented. The valence electron spectrum and the core level spectra including the associated satellite structures from the Cr, C, and O atoms are discussed. Comparison to free CO and to CO adsorbed on metal surfaces are made. An assignment of the valence levels is achieved using an intensity model. The anomalous dispersion of the narrow band in CO adsorbed on Cu seems to be related to the localization properties of the corresponding 7a_lg level in Cr(CO)₆. The Cls and Ols shake-up structures are assigned using the Z + 1 approximation, electron energy loss data and data from shake-up spectra of free CO. The Cr core level binding energy shifts relative to Cr metal are shown to vary with the subshell. Electronic structure and vibronic calculations are carried out for the ground and Cls and Ols core ionized states. The results for the vibronic coupling constants and for the vibrational excitations confer more with the observations in the electron energy loss spectra of free CO rather than with the photoelectron spectra of free CO. This supports the notion of a, close to complete, charge transfer screening accompanying ligand core ionization of Cr(CO)₆.