We studied β-delayed singles-α spectra from ${}^8\mathrm{Li}$ and ${}^8\mathrm{B}$ decays with special emphasis on a careful calibration of the energy scale. ${}^8\mathrm{Li}$ and ${}^8\mathrm{B}$ activities were produced by ${}^7\mathrm{Li}$($d,p$) and ${}^6\mathrm{Li}$(${}^3\mathrm{He}$,$n$) reactions, respectively, and deposited in thin C foils. Delayed α's were counted in thin, cooled Si detectors with small solid angles to reduce summing with β's. The energy scale and detector response were calibrated with spectroscopic grade radioactive sources. We extracted the ${}^8\mathrm{Li}$ and ${}^8\mathrm{B}$ final-state continuum shapes from our spectra by using $R$-matrix analyses that included effects of lepton-recoil broadening and detector response. Our results are in excellent agreement with a recent measurement using ${}^8\mathrm{B}$'s implanted in a Si counter and in good agreement with our reanalysis of the older Wilkinson-Alburger ${}^8\mathrm{Li}$ and ${}^8\mathrm{B}$ data, but disagree with a recent ${}^8\mathrm{B}$ experiment using a coincidence technique.

• Received 16 December 2005

DOI:https://doi.org/10.1103/PhysRevC.73.055802