Influence of physical and chemical environments on the decay rates of 7Be and 40K

We measured the electron-capture decay rate of Be-7 implanted into hosts of graphite, boron nitride, tantalum, and gold. We have found that this decay rate varies by as much as 0.38% from one host to another. We also measured the electron-capture decay rate of K-40 in four different chemical compounds and as both a solid and dissolved in solution. To within our measurement precision of +/- 1 %, we have found no influence of the environment on the K-40 decay rate. The implications of these results for the solar neutrino problem and for potassium/argon dating are discussed. (C) 2001 Published by Elsevier Science B.V.