Isotope Shift in B I at 2090 Å as a Probe of Cosmic Nucleosynthesis

Determination of the cosmic abundance of the light elements Li, Be and B is critical for the understanding of how these elements have been formed in the Universe. The Standard Model for the Big Bang nucleosynthesis, which assumes a uniform density, and its complementary model, the Non-uniform Density Model (see e.g. Kajino and Boyd, 1990), differ considerably in their predictions of Be- and B-production . However, recent determinations of the abundance of Be (Gilmore et al. 1991) and B (Duncan et al. 1992) in metal-poor stars are orders of magnitude larger than those predicted from any Big Bang nucleosynthesis model. The isotopes 9Be, 10B and 11B are therefore thought to have been produced by cosmic spallation, primarily when high-energy protons and α-particles collide with CNO nuclei in the interstellar medium.