\label{fig:pes_sheme}
Scheme illustrating the mask method for the calculation of electron photoemission.
A mask function (a) is used to effectively split each Kohn-Sham orbital into bounded and unbounded
components localized in different spatial regions $A$ and $B$ according to the diagram in (b). 
In $A$ the states are represented on a real-space grid while in $B$ they are described in momentum space.
A striped region indicates the volume where the two representations overlap.
The propagation scheme of eqs.~\eqref{eq:FMM_prop} and~\eqref{eq:FMM_prop_aux} allows seamless transitions from one representations to the other and
is capable to describe electrons following closed trajectories like the one in (b).