The relative distribution of isotopes produced during the big bang is a sensitive probe of cosmology. Uncertainties remain in the nuclear reactions between deuterium and ${}^7\mathrm{Be}$, which lead to a reduction in the ${}^7\mathrm{Li}$ yield. In two experiments using the ${}^{10}\mathrm{B}({}^3\mathrm{He},\alpha ){}^9\mathrm{B}$ reaction, the spectrum of ${}^9\mathrm{B}$ states above the deuteron threshold was investigated with the SE-SPS spectrograph and their decay through $\alpha , \mathrm{d}$, or $\mathrm{p}$ emission observed in coincidence with the SABRE silicon detector array. The dominant ${}^7\mathrm{Be}+\mathrm{d}$ resonance was measured at 299(13)-keV center-of-mass energy, and its decay branching ratios were determined. This resonance energy and resonance strength of 1.7(4) keV correspond to higher reaction rates and smaller uncertainties than a previous experiment, but do not alter the big-bang nucleosynthesis yield for ${}^7\mathrm{Li}$ significantly. An additional tentative peak at 150(12) keV was observed, but could not conclusively be attributed to the ${}^7\mathrm{Be}+\mathrm{d}$ channel and was not observed in other channels.

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• Big bang nucleosynthesis
• Nuclear astrophysics
• Nuclear reaction rates
• Resonance reactions
• 6 ≤ A ≤ 19