Search for nucleosynthetic and cosmic-ray induced gamma-ray lines from the Galactic plane.

We have combined all OSSE spectra of the central radian of the Galaxy obtained through the end of 1994. These data have been searched for evidence of diffuse emission of nucleosynthetic gamma-ray lines (Na-22, 1.275 MeV: Fe-60, 1.17 and 1.33 MeV) and cosmic-ray induced gamma-ray lines (de-excitation of C-12*, 4.44 MeV, and of O-16*, 6.13 MeV). We have looked in detail at possible systematic errors in the line measurements. Our preliminary results show no evidence for the presence of either broad or narrow cosmic-ray induced lines, nor for emission from Na-22, down to 3 sigma upper limits similar or equal to 2 10(-4)gamma/(cm(2)-sec-rad). We find weak evidence (approximate to 2 sigma) of Fe-60 line emission from positive Galactic longitudes in the central radian.