Precise study of the final-state continua in 8Li and 8B decays

We studied beta-delayed singles-alpha spectra from Li-8 and B-8 decays with special emphasis on a careful calibration of the energy scale. Li-8 and B-8 activities were produced by Li-7(d,p) and Li-6(He-3,n) reactions, respectively, and deposited in thin C foils. Delayed alpha's were counted in thin, cooled Si detectors with small solid angles to reduce summing with beta's. The energy scale and detector response were calibrated with spectroscopic grade radioactive sources. We extracted the Li-8 and B-8 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 B-8's implanted in a Si counter and in good agreement with our reanalysis of the older Wilkinson-Alburger Li-8 and B-8 data, but disagree with a recent B-8 experiment using a coincidence technique.