Precision branching ratio measurement for the superallowed β+ emitter 62Ga and isospin-symmetry-breaking corrections in A ≥ 62 nuclei

A high-precision branching ratio measurement for the superallowed beta(+) decay of Ga-62 was performed at the Isotope Separator and Accelerator radioactive ion beam facility. Nineteen gamma rays emitted following beta(+) decay of Ga-62 were identified, establishing the dominant superallowed branching ratio to be (99.861 +/- 0.011)%. Combined with recent half-life and Q-value measurements, this branching ratio yields a superallowed ft value of 3075.6 +/- 1.4 s for Ga-62 decay. These results demonstrate the feasibility of high-precision superallowed branching ratio measurements in the A >= 62 mass region and provide the first stringent tests of the large isospin-symmetry-breaking effects predicted for these decays.