High-precision branching ratio measurement for the superallowed β+ emitter Ga62

A high-precision branching ratio measurement for the superallowed beta(+) decay of Ga-62 was performed at the Isotope Separator and Accelerator (ISAC) radioactive ion beam facility. The 8 pi spectrometer, an array of 20 high-purity germanium detectors, was employed to detect the gamma rays emitted following Gamow-Teller and nonanalog Fermi beta(+) decays of Ga-62, and the SCEPTAR plastic scintillator array was used to detect the emitted beta particles. Thirty gamma rays were identified following Ga-62 decay, establishing the superallowed branching ratio to be 99.858(8)%. Combined with the world-average half-life and a recent high-precision Q-value measurement for Ga-62, this branching ratio yields an ft value of 3074.3 +/- 1.1 s, making Ga-62 among the most precisely determined superallowed ft values. Comparison between the superallowed ft value determined in this work and the world-average corrected (Ft) over bar value allows the large nuclear-structure-dependent correction for Ga-62 decay to be experimentally determined from the CVC hypothesis to better than 7% of its own value, the most precise experimental determination for any superallowed emitter. These results provide a benchmark for the refinement of the theoretical description of isospin-symmertry breaking in A >= 62 superallowed decays.