A comparative study of theoretical methods for the analysis of high‐resolution double‐charge‐transfer spectra, applied to the ethene molecule

The low-energy electronic states of the ethene dication are investigated theoretically, a comparison being made between the predictions of the ab initio ADC(2) Green's function method and of the recently developed semi-empirical MSXα method. Both methods provide a consistent unambiguous analysis of the closely-spaced peak structure recently observed in a high-resolution double-charge-transfer spectrum for the ethene molecule.