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7 li, the primordial isotope of lithium, was produced in Big Bang nucleosynthesis about half an hour after the birth of the universe. Lithium is a very light metal and is used today in lithium-ion batteries, in fluoride coolant for molten salt reactors (MSRs), and as a source of tritium for nuclear fusion.
The 7 li problem is a serious one, and it has repercussions for cosmological models and our understanding of the evolution of the universe. It is a major source of uncertainty in the BBN model, and if eliminated could have a large impact on the predictions of the baryon-to-photon ratio e and subsequently the primordial abundances of light nuclides heavier than 7Li.
Several key nuclear reactions destroy 7Li, but the reaction rate is still an unsolved issue due to limited experimental information on energy levels near the threshold in 9Be. A series of important experiments for these reactions have been carried out in the past few years, and a significant improvement in our knowledge of their rates has been achieved.
In this article, we propose a new way to study the nuclear reaction rate of 7Li(d,n)24He, which has been considered to be an important 7Li destruction reaction. The reaction rate of this reaction is evaluated by a systematic study that includes the contribution from direct components and resonances near the deuteron threshold.
The 7Li(d,n)24He reaction is found to be more efficient than previously thought for temperature ranges above T9 = 0.07, resulting in about a 10% increase in the final primordial abundance of light nuclides with A > 7. This is mainly caused by the increased number of reactions regulated by 7Li, and it leads to a 40% increase in the primordial abundance of light nuclides heavier than 7. We also examine the temporal variation in seawater d7Li to reconstruct its influence on continental records, and we find that it rises by 9% during the Cenozoic.