hesis (SBBN) describes the formation of the lightest elements by a sequence of reactions (see Fig. 1) and predicts their abundances as a function of baryon density. Therefore, a comparison between the [...] 7 Li abundances in old stellar objects allows to constrain the baryon to photon density η=n B /n γ [1] (see Fig. 2). So far, only the abundances of 2 H, 3 He, 4 He, and 7 Li could be used because of the [...] At GSI we investigated the 14 C(n,γ) 15 C reaction with the Coulomb dissociation method. References [1] B.D. Fields and S. Sarkar, astro-ph/0601514, 2006 [2] M. Asplund et al., astro-ph/0510636, 2005 [3]