Both the XES and XSS data for [Fe(bmip) 2 ] 2+ photoexcited at 400 nm show oscillations with the same period of 278 fs and an exponential damping time constant of 500 fs. The XSS oscillations clearly identify coherent vibrational motion along the Fe-N/ Fe-C stretching nuclear coordinate. Interestingly, the breathing vibration is also reflected in the oscillatory XES signal 29 ; based on the XES data, the coherent vibrations were assigned to the 3 MC states. Figure displays the nuclear dynamics averaged over all trajectories (400 nm excitation case) along the Fe-N and Fe-C bonds, as well as projected onto the breathing normal mode ν 14 . In agreement with the XES/XSS experiments and their assignments, in our simulations, we observe coherent oscillations along the breathing mode with a period of ∼300 fs, which is clear in the Fe-C, but less in the Fe-N bond lengths (in the latter, the oscillations are dominated by faster components). Metal-ligand bonding and covalency has recently been proposed to be a key factor in rationalising the remarkable sensitivity of core-to-core XES to structural changes . Namely, the Fe-ligand interaction modulates the screening of the relevant core holes (e.g., 1s and 2p, for Kα); as this modulation varies with the Fe-ligand distance, the structural dynamics will be reflected in the time-dependent XES signal. Our results also indicate the importance of covalency, as we clearly observe the coherent oscillations with a period reasonably matching the experimental one for the Fe-C bonds, which are significantly more covalent than the Fe-N. We note that i) the coherent oscillations are very similar for the case of 485 nm excitation (see ESI, Figure ), and ii) damping (decoherence) of our oscillations is slower than the experimental one; we attribute this discrepancy to the underestimation of intermode interactions and the absence of solvent in our model. It is important to stress, however, that the appearance of vibrational coherence and the period of oscillations is in good agreement with XES/XSS experiments, and decoherence does occur, even if it is slower than observed experimentally. Finally, we analyse the origin of the observed vibrational coherence and the case of TOAS experiment with 485 nm excitation. The vibrational dynamics along the Fe-N/Fe-C bonds are triggered by electronic structure changes in the 3 MC states, dominated by the population of an antibonding e * g orbital (d x 2 -y 2 or d z 2 combined with the corresponding ligand orbitals). Any considerable contribution of MLCT states to such dynamics along the breathing mode (see Figure ) is ruled out, since an MLCT excitation does not lead to significant changes in the Fe-N/Fe-C bond lengths (i.e., the case of nested ground-state and 3 MLCT oscillators 20 , see also Figure ). As seen in Figure , the 3 MC population rises fast, within an oscillation period of the breathing mode (∼300 fs), hence vibrational coherence is preserved, as evidenced by the observation of coherent oscillations (Figure ). Therefore, the appearance of coherent oscillations, with a period matching the vibrational period of the breathing mode, can be used as a fingerprint for any significant 3 MC component. Importantly, the TOAS data also contain oscillations with a rather similar period to those obtained by XES and XSS (see ref. 13, ESI), appearing already at ∼300 fs. Given the connection between the 3 MC population rise and the coherent oscillations, this clearly means that the 3 MC states have to be populated already at early times (∼100-300 fs), otherwise the coherent oscillations could not have been observed. All this agree excellently with our simulated dynamics, unambiguously evidencing the existence of the observed early sub-ps 3 MC component and thus the branching mechanism of excited-state population into 3 MLCT and 3 MC.