Interpretation of the ionization spectra of the cyanomethanes: CH 3CN, CH 2(CN) 2 and C(CN) 4

Abstract

The valence ionization spectra of the mono-, di- and tetra-cyanomethane molecules are computed by Green function methods. As previously experienced on other cyano-derivatives of organic molecules, a hole-mixing effect is found. A partial reassignment of the spectrum is possible in the case of CH 2(CN) 2, whereas, due to the compactness of the spectrum and to the limitation of the basis set, an unambiguous assignment is not possible for C(CN) 4. The Koopmans ordering of the IP's is modified in two cases by the many-body perturbation.