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

We studied β-delayed singles-α spectra from 8Li and 8B decays with special emphasis on a careful calibration of the energy scale. 8Li and 8B activities were produced by 7Li(d,p) and 6Li(3He,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 8Li and 8B 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 8B's implanted in a Si counter and in good agreement with our reanalysis of the older Wilkinson-Alburger 8Li and 8B data, but disagree with a recent 8B experiment using a coincidence technique