ΔT=1,0+→0+beta decay ofMg28

The isospin-forbidden beta-decay branching ratio of the $0^{+}$, $T=2\mathrm{}$ ${}_{}{}^{28}{}_{}{}^{}\mathrm{Mg}$ ground state to the 972-keV $0^{+}$, $T=1\mathrm{}$ level of ${}_{}{}^{28}{}_{}{}^{}\mathrm{Al}$ is measured to be (0.31 ± 0.04)% corresponding to $ft=(9.20\mathrm{}\pm 1.1)\times {10}^7$s, $logft=7.96\mathrm{}\pm 0.06$. A charge-dependent matrix element between the $0^{+}$, $T=2\mathrm{}$ analog state at 5992 keV in ${}_{}{}^{28}{}_{}{}^{}\mathrm{Al}$ and the anti-analog level at 972 keV of 20.6 ± 1.6 keV is deduced from this branching ratio. This is in good agreement with a previous result.