  Attosecond pump-probe ionization process can be used to prepare atomic ions
in the coherent superposition of states with opposite parity. The multiphoton
shake-up ionization of Helium, in particular, generates ions with same
principal quantum number and a net dipole moment that evolves on a time scale
of few picoseconds, due to spin-orbit coupling. In this work we use an ab
initio time-dependent close-coupling code to study how the coherence between
levels of Helium ion can be controlled from the parameters of the
ionizing-pulse sequence. The observed periodic revivals, on a picosecond time
scale, of the ion dipole moment gives access to the study of the ionization of
oriented targets.
