The angle-resolved N 1s photoelectron spectrum of has been measured with high resolution in the threshold region. An analysis of the vibrational fine structure yields a vibrational energy of and a lifetime broadening of for the core-ionized molecule. As in the case of C 1s ionization of CO, the vibrational fine structure changes considerably with photon energy in the region of both the shape resonance and the double excitations. Both the vibrationally resolved partial photoionization cross sections and asymmetry parameters have been determined in this photon energy range. The calculated cross sections in the literature are in reasonable agreement with experiment. In addition, we have measured the cross sections and asymmetry parameters of the most intense direct and conjugate shake-up satellites. The behaviour of the satellites is found to differ significantly from that of the corresponding C 1s satellites of CO.

The absolute photoabsorption cross section of benzene (C6H6), encompassing the C 1s−1 π*e2u resonance, the C 1s threshold, the satellite thresholds, and extending up to 800 eV, has been measured using synchrotron radiation. Measurements of the discrete absorption structure from below the C 1s ionization threshold have been performed at high resolution. In order to unambiguously assign all structure present in the photoabsorption cross section, C 1s photoelectron spectra were measured from the C 1s threshold region up to 350 eV along with satellite spectra. The C 1s−1 single-hole and the satellite cross sections have been derived in absolute units, and their angular distributions have been determined. Resonant and normal Auger spectra were taken on the main features of the photoabsorption and single-hole cross sections. From the best resolved photoelectron spectra the underlying structure in the asymmetric benzene photoelectron peak can be partly disentangled. The experimental data show that at least two vibrational modes play a role in the C 1s photoelectron spectrum. The behavior of the investigated shake-up structure closely resembles that of ethene and ethyne, where the satellite bands due to π→π* excitations gain intensity towards threshold, an observation which may be attributed to conjugate shake-up processes. These processes lead to a significant contribution of the satellite intensity to the production of the absorption features traditionally assigned to the carbon shape resonances in benzene. An EXAFS analysis of the wide range oscillations present on the photoabsorption cross section has been performed, and reveals the C–C nearest-neighbor distance.

The 3d photoelectron spectrum of xenon has been measured at several photon energies in the immediate threshold region. The absolute photoionization cross section and angular anisotropy parameter ␤ have been determined for the two spin-orbit-split components. The experimental results are compared with calculations using a relaxed single-channel approximation. In agreement with theory, most abrupt changes in cross section and angular distribution are observed just above threshold. However, the Xe 3d 5/2 photoionization cross section also reveals, some 30-eV above threshold a second maximum that has not been predicted theoretically.

The resonant Auger spectrum of CO has been measured at both the C and O K-edges. At the C resonance the decay spectrum was recorded selectively at the energies of the = 0, 1 and 2 vibrational states. Vibrational fine structure was not only resolved on the participator but also on the spectator lines. For the O resonance the photon energy bandwidth was sufficiently low that different, vibrationally distinct regions of the absorption profile could be selected. Ab initio calculations and their detailed analysis are presented for both the C and O decay spectra. At the C resonance the calculation explicitly accounts for the vibrational fine structure including vibrational-lifetime interference effects. The appearance of the spectator part of the spectrum is shown to be strongly influenced by the existence of unbound states and diabatic interactions. The nodal structure of the vibrational wavefunction of the core-excited state is reflected in the decay spectrum.

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