Abstract
The N1s (NO2) ESCA spectrum of paranitroaniline (PNA) is analyzed theoretically and experimentally. New monochromatized high-resolution spectra in the vapor (gas) and condensed phases are presented. In the condensed phase spectrum two distinct peaks are discerned, whereas the gas phase spectrum shows a drastically different feature in which the two peaks are reduced to an asymmetric band. The gas phase spectrum has been interpreted based on large-scale MCSCF wave functions calculated using a complete configuration expansion in the π valence orbital space. Emphasis is placed on the identification of features due to ’’shake’’ effects. Multiple excitations in the charge transfer excited states, as well as configuration near-degeneracy effects in the NO2 group, are found to be crucial for this identification. Our results are different from an earlier many-body, Green’s function, treatment of PNA. We find that the charge transfer shake states lie higher in energy (shakeup) and not lower (negative shakeup).
Published Version
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