Precise measurements of half-lives and branching ratios for the $ \beta$ β mirror transitions in the decay of 23Mg and 27Si

Abstract

Half-lives and branching ratios for the two mirror $ \beta$ decays of$^{23}$Mg and$^{27}$Si have been measured at the University of Jyvaskyla with the IGISOL facility. The results obtained, $ T_{1/2}=11.303(3)$ s and $ T_{1/2}= 4.112(2)$ s for the half-lives of$^{23}$Mg and$^{27}$Si , respectively, are 7 and 8 times more precise than the averages of previous measurements. The values obtained for the super-allowed branching ratios of$^{23}$Mg and$^{27}$Si are $ B.R.=92.18(8)\%$ and $ B.R.=99.74(2)\%$ , respectively. The result for$^{23}$Mg is three times more precise than the average of the previous measurements, while for$^{27}$Si the precision has not been improved, the average of the previous measurements being already very precise. Isospin-symmetry-breaking corrections have been calculated for the two nuclei to determine the corrected $ {F}t$ value.