  We consider wave propagation and scattering governed by one dimensional
Schrodinger operators with truncated periodic potentials. The propagation of
wave packets with narrow frequency supports is studied. The goal is to describe
potentials for which the group velocity (for periodic problem) is small and the
transmission coefficient for the truncated potential is not too small, i.e. to
find media where a slowing down of the wave packets coexists with a
transparency.
