Theoretical<i>K</i>-shell ionization spectra of N2 and CO by a fourth-order Green’s function method

Abstract

A recently developed complete fourth-order Green’s function method referred to as ADC(4) was used to calculate ionization energies and relative intensities of 1s hole states in N2 and CO. Very accurate 1s electron binding energies and a good qualitative description of the shakeup spectra at low and medium energies have been obtained. For the N1s and C1s results comparison is made with previous large-scale configuration interaction treatments. New results are presented for the O1s shakeup spectrum of CO. Here striking differences with respect to the C1s spectrum are found which are explained in terms of charge–transfer effects induced by electronic excitation. We also present results for shakeup states of symmetries other than 2Σ+ which are not observed in the usual photoemission experiment.