High-precision branching-ratio measurement for the superallowed β+ emitter 26Alm

A high-precision branching-ratio measurement for the superallowed beta(+) emitter Al-26(m) was performed at the TRIUMF-ISAC radioactive ion beam facility. An upper limit of <= 12 ppm at 90% confidence level was found for the second forbidden beta(+) decay of Al-26(m) to the 2(1)(+) state at 1809 keV in Mg-26. An inclusive upper limit of <= 15 ppm at 90% confidence level was found when considering all possible nonanalog beta(+)/EC decay branches of Al-26(m), resulting in a superallowed branching ratio of 100.0000(-0.0015)(+0)%.