3He(α,γ)7Be cross section at low energies

The flux of Be-7 and B-8 neutrinos from the Sun and the production of Li-7 via primordial nucleosynthesis depend on the rate of the He-3(alpha,gamma)Be-7 reaction. In an extension of a previous study showing cross section data at 127-167 keV center-of-mass energy, the present work reports on a measurement of the He-3(alpha,gamma)Be-7 cross section at 106 keV performed at Italy's Gran Sasso underground laboratory by the activation method. This energy is closer to the solar Gamow energy than ever reached before. The result is sigma=0.567 +/- 0.029(stat)+/- 0.016(syst) nb. The data are compared with previous activation studies at high energy, and a recommended S(0) value for all He-3(alpha,gamma)Be-7 activation studies, including the present work, is given.