Anomalous Epsilon Decay Branching Ratios

E/B decay branching ratios were measured for decays from Eu, 14 3 1 4 39 Sm', and 1 4 39Gd y -y triple coincidence experiments were performed


to get relative positron feedings to respective daughter levels. X-y coincidence measurements were done for 1459Gd decay to obtain relative electron capture feedings and these feedings were inferred from singles intensities for 143Eu and 1439Sm decay. 143 The decay schemes of Eu and 1439Sm were also studied, and 12 143 levels were reported in Pm as well as 16 levels in 143Sm. Data were also gathered relevant to 14ompm decay and a B+ endpoint for 66Ga decay is reported.


B decay theory is discussed in somedetail, especially concerning the implications of E/B decay branching ratios. It is shown that anomalous ratios can only occur for higher order terms 'in allowed


transitions or if a pseudoscalar force is present. Neither possibilities were hitherto eliminated experimentally. Among 15 measured /B branching ratios, two were significantly anomalous. The transition to the 808.5 keV level in 145Eu was anomalous by a factor of 24 and the transition to the 1173.1 keV level in 143Pm was anomalous by a factor of 4.9. Each case'involved a similar hindered.