Abstract
We derived model atmosphere parameters (Te ,l ogg ,( Fe/H),Vt) for 90 metal{decient stars ( 0:5 1:5, when the matter of the Galaxy is suciently homogeneous. The analysis of n-capture element abundances conrms the jump in (Ba/Fe) at (Fe/H)= 2:5. Some stars from our sample at (Fe/H) < 2: 0s how a large scatter of Sr, Ba, Y, Ce. This scatter is not caused by the errors in the measurements, and may reflect the inhomogeneous nature of the prestellar medium at early stages of galactic evolution. The matching of (Ba/Fe), (Eu/Fe) vs. (Fe/H) with the inhomogeneous model by Travaglio et al. (2001a) suggests that at (Fe/H) < 2:5, the essential contribution to the n-rich element abundances derives from the r-process. The main sources of these processes may be low mass SN II. The larger dispersion of s-process element abundances with respect to -rich el- ements may arise both from the birth of metal{poor stars in globular clusters with following dierent evolutionary paths and (or) from dierences in s-element enrichment in Galaxy populations.
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