Study of the dependence of 198 Au half-life on source geometry

We report the results of an experiment to determine whether the half-life of 198 Au depends on the shape of the source. This study was motivated by recent suggestions that nuclear decay rates may be affected by solar activity, perhaps arising from solar neutrinos. If this were the case then theβ-decay rates, or half-lives, of a thin foil sample and a spherical sample of gold of the same mass and activity could be different. We find for 198 Au, (T1/2)foil/(T1/2)sphere = 0.999±0.002, where T1/2 is the mean half-life. The maximum neutrino flux at the sample in our experiments was several times greater than the flux of solar neutrinos at the surface of the Earth. We show that this increase in flux leads to a significant improvement in the limits that can be inferred on a possible solar contribution to nuclear decays. Keywords: Beta decays, Neutrinos, Nuclear Decay Lifetimes Extensive research has shown that the decay rate of a radioactive nucleus is independent of its environment, except in those instances involving electron capture, internal conversion, or high external magnetic fields [1]. Therefore, it is surprising that a recent series of papers [2, 3, 4, 5, 6] have raised the question