First detection of 7Li/6Li-ratio in the interstellar medium beyond the solar-system, and its impact on primordial 7Li Original Research Article

We determine primordial 7Li abudance independently of a previous method based on the measurement of the Spite plateau by using isotopic abundance ratios of 7Li/6Li in the interstellar media. The inferred best fit constraints on the primordial 7Li abundance is 7Li/H≅ 2.5 × 10−10, and the conservative upper limit at the 95% confidence level turns out to be 7Li/H < 8 × 10−10.