  Exposing a molecule to intense light pulses may bring this molecule to a
nonstationary quantum state, thus launching correlated dynamics of electronic
and nuclear subsystems. Although much had been achieved in the understanding of
fundamental physics behind the electron-nuclear interactions and dynamics,
accurate numerical simulations of light-induced processes taking place in
polyatomic molecules remain a formidable challenge. Here, we review a recently
developed theoretical approach for evaluating electronic coherences in
molecules, in which the ultrafast electronic dynamics is coupled to nuclear
motion. The presented technique, which combines accurate ab initio on-the-fly
simulations of electronic structure with efficient semiclassical procedure to
compute the dynamics of nuclear wave packets, is not only computationally
efficient, but also can help shed light on the underlying physical mechanisms
of decoherence and revival of the electronic coherences driven by nuclear
rearrangement.
