(a) Experimental x-ray absorption spectrum of recorded in the vicinity of the O ionization threshold. Photon energies used for the recording of resonant Auger electron spectra are marked by arrows and labeled A, B, C, and D, respectively. The absolute energy scale has been established according to Ref. 1; (b) theoretical x-ray absorption spectrum calculated by the four-crossing model (see text for further details). The absolute theoretical energy scale was shifted by about in order to match the experimental spectrum.
(a) Experimental resonant Auger electron spectra of for excitation energies marked by arrows in Fig. 1(a); (b) theoretical resonant Auger spectra calculated by the four-crossing model (see text for further explanations); the direct channel is included with and .
(a) Transition dipole moment matrix elements based on the potential curves from Fig. 4(b) (four-crossing model); (b) Decay matrix elements based on the potential curves from Fig. 4(b) (four-crossing model). The vertical dotted line indicates of the ground state.
(a) Diabatic potential curves calculated as discussed in the text (cf. Sec. IV B); (b) Mixed adiabatic/diabatic potential curves of the four-crossing model. The vertical dotted line indicates of the ground state.
(a) Theoretical x-ray absorption spectrum based on the diabatic model; (b) theoretical x-ray absorption spectrum based on the two-crossing model. (see text for further explanations). The absolute theoretical energy scale was shifted by about in order to match the experimental spectrum.
Estimate of vibronic coupling (VC) effect in the four-crossing model. The partial vibrational profile [marked as “partial LZ ”] is weighted by Landau-Zener (LZ) probabilities [cf. Eq. (9)] of propagation in the bound adiabatic state. The labels “adiabatic” and “LZ” mark total XAS spectra computed in adiabatic approximation and taking into account the LZ factor ; .
Comparison of the partial resonant Auger scattering cross sections and (upper panel) with the total cross section which includes the interference term (lower panel) for detuning, [cf. experimental spectrum C from Fig. 2(a)]. The direct photoionization channel is not included.
Total resonant Auger scattering cross sections where the direct channel is included, , .
Calculated electronic interaction of different core-excited states at the corresponding crossing points (in a.u.). Crossings between Rydberg states are not included.
Ratio between the matrix elements of the dipole moment and the decay operator of the diabatic core-excited states, computed at the ground-state equilibrium geometry.
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