Abstract
Lithium is one of the few primordially produced elements. The value of the primordial Li is taken to be that observed in metal-poor dwarfs, where it is not contaminated by stellar Li sources that act on longer timescales. The atmospheric abundance is currently derived from the Li I λ6707 resonance transition, and the validity of the models employed has been questioned (Kurucz). In this Letter, we report the first detection of the Li I λ6104 2 2P-3 2D subordinate transition in the prototype Population II star HD 140283. The same Li abundance of (Li/H)=1.4×10−10 is found to be consistent with both the resonance and subordinate lines. The two lines form at different depths in the atmosphere, implying that the one-dimensional, homogeneous atmospheric models used in the abundance determination are essentially correct. When coupled with the standard big bang yields, the Li in the halo dwarfs provides two solutions for the baryon-to-photon ratio η10=nb/n×1010 and for the present baryon density Ωbh270=0.0748η10: a first solution at η10 ≈ 1.8, which is consistent with the η10 implied by the high deuterium values D/H ≈ 2×10−4 observed in some quasar absorption systems (Webb et al.); and a second solution at η10 ≈ 4, which is consistent, within the errors, with the low deuterium D/H=3.4×10−5 measured in other quasar absorption systems (Burles & Tytler).
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