Electron-capture to positon-emission ratio in the decay of 22Na

Abstract

The electron-capture to positon-emission ratio of 22Na has been measured as e/ β + = 0.1048±0.0007. This ratio has also been calculated using the corresponding transition probabilities; (e/ β +) calc. = 0.1138±0.0025 (omitting the correction for orbital electron exchange) and 0.100±0.006 (including electron exchange). Comparison of the measured and calculated branching ratios yields b = (−2.4±0.9) × 10 −2 m 0 c 2 (omitting electron exchange) and (1.5±3.7) × 10 −2 m 0 c 2 (including electron exchange) for the Fierz interference term. Assuming zero Fierz interference, as indicated by many other measurements, our results yield strong evidence for orbital electron exchange effects.