B. Kempgens

Vibrationally resolved decay spectra of CO at the C and O K-edges: experiment and theory

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.

Constant initial state (CIS) spectroscopy in the study of the decay of core-to-bound resonances in N2

Constant initial state (CIS) photoemission spectra of the N2 1u-1 and 3g-1 states have been measured in the photon energy range corresponding to the N 1s* core-to-bound transition, where they acquire intensity from participator decay. The resolution was sufficiently high that the spectra could be recorded individually for the first four vibrational components of the 1u-1 state and for the first two vibrational components of the 3g-1 state. Differences in the spectra for these two final states are discussed in terms of their potential curves compared to that of the intermediate neutral excited state. We point out the potential usefulness of the CIS method for elucidating the details of the molecular potential.

The C 1s Auger decay spectrum of : an analysis of the core-excited states

Auger spectra of the molecule have been measured at various photon energies corresponding to the excitation of a C 1s electron into the valence and Rydberg orbitals. The decay spectrum at the resonance shows one relatively weak participator transition that involves the bonding orbital. Extra features observed at kinetic energies higher than the spectator transitions are tentatively attributed to Auger decay in fragments which are produced by dissociation of the core-excited molecule. Core-excited Rydberg states are found to decay almost exclusively via spectator transitions. The use of the ratio participator-to-total decay as a probe for the strength of valence-Rydberg orbital mixing is called into question.