Negative shake-up energy in core ionization

It is shown that the dynamical screening phenomena, which have recently been found to affect the shape of adsorbate core-hole spectra, occur also in the core ionization of certain molecules. For K-shell ionization of paranitroaniline we find shake-up transitions of negative energy which cause a multipeak structure of the corresponding line in the ESCA (electron spectroscopy for chemical analysis) spectrum. The present first-principles results lead to a new interpretation of the origin of the dynamical screening processes in adsorbates.