Figure 4: Ultrafast Auger probe simulations.

Calculated Auger decay spectra using the CK-CIS method (see Supplementary Note 1) for the ground-state GS, the n π* and π π* (a–c), states (see Supplementary Tables 1–6 for more information on prominent Auger decay features). (a) The ground-state Auger decay is calculated at its minimum energy geometry and corresponds to the Auger decay of a non-UV excited molecule. (b) The π π* state is evaluated at the Frank–Condon geometry and the π π* minimum geometry according to ref. 19. While the spectrum of O(7) does not shift with respect to the ground state, the O(8) spectrum shifts blue in the π π* minimum because of the C(4)-O(8) stretch. (c) The simulation predicts a redshift for n π* states, which once more is only due to the O(8) spectrum. Other geometries on the respective state confirm the trend (see Supplementary Fig. 1). The vibrationally hot electronic ground state in (d) calculated by the ADC(2) method via averaging different nuclear geometries (see Supplementary Fig. 2) broadens the Auger spectrum with respect to the the ADC(2) simulation of the ‘cold’ ground state for reference. (e) Experimental difference spectra cut at two different times from Fig. 2a (lower part) indicating a shift towards higher kinetic energy at early times and lower kinetic energies later.