A core-level photoionization study of furan

We have measured the vibrationally resolved C 1s photoelectron spectrum of the aromatic heterocycle furan (C4H4O). The vibrational profile appears to be dominated by a low-frequency mode, which shows an unusually high degree of excitation for ionization of the C atoms furthest from the oxygen. Our experimental results are compared with calculations, which reveal that several different vibrational modes participate in the vibrational pattern. A well resolved C 1s satellite spectrum at a photon energy of 335 eV has also been measured, and is compared to previous experimental and theoretical results. In a separate experiment the partial electron yield (“absorption”) spectrum has been obtained in the region from just below the C 1s π* resonance up to the respective ionization thresholds. A new high intensity feature has been identified on the high-energy flank of the C 1s−1π(3b1)* resonance. With the aid of resonant Auger spectroscopy we have tentatively assigned this feature to a Rydberg resonance. We also present the C 1s and O 1s Auger spectra of furan.