Measurement of the full excitation spectrum of the 7Li(p, γ)αα reaction at 441 keV

A current challenge for ab initio calculations is systems that contain large continuum contributions such as Be-8. We report on new measurements of radiative decay widths in this nucleus that test recent Green's function Monte Carlo calculations. Traditionally, gamma ray detectors have been utilized to measure the high energy photons from the Li-7(p, gamma) alpha alpha reaction. However, due to the complicated response function of these detectors it has not yet been possible to extract the full gamma ray spectrum from this reaction. Here we present an alternative measurement using large area Silicon detectors to detect the two alpha particles, which provides a practically background free spectrum and retains good energy resolution. The resulting spectrum is analyzed using a many-level multi channel R-matrix parametrization. Improved values for the radiative widths are extracted from the R-matrix fit. We find evidence for significant non-resonant continuum contributions and tentative evidence for a broad 0(+) resonance at 12 MeV. (C) 2018 The Authors. Published by Elsevier B.V.