Density matrix based time-dependent configuration interaction approach   to ultrafast spin-flip dynamics
  Recent developments in attosecond spectroscopy yield access to the correlated motion of electrons on their intrinsic time scales. Spin-flip dynamics is usually considered in the context of valence electronic states, where spin-orbit coupling is weak and processes related to the electron spin are usually driven by nuclear motion. However, for core-excited states, where the core hole has a nonzero angular momentum, spin-orbit coupling is strong enough to drive spin-flips on a much shorter time scale. Using density matrix based time-dependent restricted active space configuration interaction including spin-orbit coupling, we address an unprecedentedly short spin-crossover for the example of L-edge (2p$\rightarrow$3d) excited states of a prototypical Fe(II) complex. This process occurs on a time scale, which is faster than that of Auger decay ($\sim$4\,fs) treated here explicitly. Modest variations of carrier frequency and pulse duration can lead to substantial changes in the spin-state yield, suggesting its control by soft X-ray light. 
H. Wang, S. I. Bokarev, S. G. Aziz, O. K\"uhn
physics.atm-clus physics.chem-ph