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

We measured the electron-capture decay rate of 7Be 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 40K 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 40K decay rate. The implications of these results for the solar neutrino problem and for potassium/argon dating are discussed.