Identification of transitions into Rydberg states in the X-ray absorption spectra of condensed long-chain alkanes

A detailed theoretical analysis of the high-resolution X-ray absorption spectra of condensed long-chain alkane molecules (hexatriacontane, C36H74 and heptatriacontane, C37H76) suggests that the resonance at 287.7 eV, which is the dominating feature in the near-edge X-ray absorption spectra of saturated long-chain hydrocarbons, is due to transitions into Rydberg states. These findings, which are at variance with the previous interpretation, are corroborated by the identification of a previously unresolved resonance at 288.2 eV in the high-resolution X-ray absorption spectra and of the observation of a strong quenching of the X-ray absorption resonances upon physisorption on a Cu(lll)-metal surface.