A high-precision branching ratio measurement for the superallowed ${\beta }^{+}$ decay of ${}^{62}\mathrm{Ga}$ was performed at the Isotope Separator and Accelerator (ISAC) radioactive ion beam facility. The 8π spectrometer, an array of 20 high-purity germanium detectors, was employed to detect the γ rays emitted following Gamow-Teller and nonanalog Fermi ${\beta }^{+}$ decays of ${}^{62}\mathrm{Ga}$, and the SCEPTAR plastic scintillator array was used to detect the emitted β particles. Thirty γ rays were identified following ${}^{62}\mathrm{Ga}$ 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 ${}^{62}\mathrm{Ga}$, this branching ratio yields an $\mathit{ft}$ value of $3074.3\pm 1.1$ s, making ${}^{62}\mathrm{Ga}$ among the most precisely determined superallowed $\mathit{ft}$ values. Comparison between the superallowed $\mathit{ft}$ value determined in this work and the world-average corrected $\overline{\mathcal{F}t}$ value allows the large nuclear-structure-dependent correction for ${}^{62}\mathrm{Ga}$ 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-symmetry breaking in $A⩾62$ superallowed decays.

• Received 25 April 2008

DOI:https://doi.org/10.1103/PhysRevC.78.025502