  We consider photo ionization of an atom which, due to passing through a
diffraction grating, is prepared in a multi-site state possessing a periodic
space structure with alternating maxima and minima. It has been found that this
process qualitatively differs from photo ionization of a 'normal' atom. In
particular, the spectra of emitted electrons and recoil ions in this process
display clear one- and two-particle interference effects. Moreover, there are
also striking differences between the momentum distributions of these
particles, which no longer mirror each other. The origin of all these features
is discussed in detail. It is also shown that the information about the
diffraction grating, which is encoded in the multi-site state of the atom, can
be fully decoded by exploring the spectra of recoil ions whereas the
photo-electron spectra contain this information only partially.
