Precision measurement of the decay rate of Be-7 in host materials

A controlled and precise determination of the cross sections of the fusion reactions Be-7(p,gamma)B-8 and He-3(He-4,gamma)Be-7, which play an important role in determining the solar neutrino flux, necessitates the knowledge of a precise value of the electron-capture half-life of Be-7. This half-life may depend on the material hosting the Be-7 atoms via small modifications of the electron density around the Be-7 nucleus. In this brief communication we report on the measurement of Be-7 implanted in four materials: copper, aluminum, sapphire, and PVC. The four results are consistent with a null host dependence within two standard deviations and their weighted average of 53.236(39) d agrees very well with the adopted value in the literature, 53.22(6) d. The present results may exhibit a slight (0.22%) increase of the half-life at room temperature for metals compared to insulators that requires further studies.