  The rapid neutron-capture process, or r-process, is known to be fundamental
for explaining the origin of approximately half of the A>60 stable nuclei
observed in nature. In recent years nuclear astrophysicists have developed more
and more sophisticated r-process models, by adding new astrophysical or nuclear
physics ingredients to explain the solar system composition in a satisfactory
way. Despite these efforts, the astrophysical site of the r-process remains
unidentified. The composition of the neutron star outer crust material is
investigated after the decompression that follows its possible ejection. The
composition of the outer crust of a neutron star is estimated before and after
decompression. Two different possible initial conditions are considered, namely
an idealized crust composed of cold catalyzed matter and a crust initially in
nuclear statistical equilibrium at temperatures around 10 GK. We show that in
this second case before decompression and at temperatures typically
corresponding to 8 GK, the Coulomb effect due to the high densities in the
crust leads to an overall composition of the outer crust in neutron-rich nuclei
with a mass distribution close to the solar system r-abundance distribution.
Such distributions differ, however, from the solar one due to a systematic
shift in the second peak to lower values. After decompression, the capture of
the few neutrons per seed nucleus available in the hot outer crust leads to a
final distribution of stable neutron-rich nuclei with a mass distribution of 80
< A < 140 nuclei in excellent agreement with the solar distribution, provided
the outer crust is initially at temperatures around 8 GK and all layers of the
outer crust are ejected. The decompression of the neutron star matter from the
outer crust provides suitable conditions for a robust r-processing of the light
species, i.e., r-nuclei with A < 140.
