Measurement of Difference in Decay Rate for 7Be in Li and 7Be in Ta

Abstract

The difference in decay rate for 7Be in Ta and 7Be in Li was measured and found to be (6.43 ± 0.76) x 10-4 wk-1, making the relative difference in decay rate ∆λ/λ = (0.71 ± 0.09)%. The probability of decay by electron capture is proportional to the density of electrons at the 7Be nucleus; therefore, 7Be nuclei in different chemical environments may decay at measurably different rates. Most previous measurements for different chemical combinations of 7Be have found ∆λ/λ to be on the order of 10-4 to 10-3. A quasi-differential counting method was used in the current experiment wherein two samples are alternately placed in front of a high-purity germanium detector (HPGe) and the number of counts recorded. A plot of the ratio of counting rates vs. time yielded a straight-line whose slope was proportional to ∆λ. The proportionality constant was determined from the intercept of this plot.