Calculation of transition metal compounds using an extension of the CNDO formalism. V. many body effects in the inner valence shell photoionization spectra of free and coordinated carbon monoxide

The inner valence shell region in the photoionization spectra of NiCO, Ni(CO)₄ and Cr(CO)₆ is studied by means of a diagonal two-particle—hole Tamm—Dancoff approximation. Many body effects are found in the energy range of the CO-ligand ionizations. The effects are more pronounced in NiCO and Ni(CO)₄ than in Cr(CO)₆. Since similar results have to be expected for adsorbate systems, the interpretation of photoemission spectra of such systems on the basis of the simple one particle picture should be handled with care.