QEC-value determination for 21Na→21Ne and 23Mg→23Na mirror-nuclei decays using high-precision mass spectrometry with ISOLTRAP at the CERN ISOLDE facility

Abstract

We report on high-precision QEC values of the 21Na→21Ne and 23Mg→23Na mirror β transitions from mass measurements with ISOLTRAP at the CERN ISOLDE facility. A precision of δm/m=9×10−10 and δm/m=1.5×10−9 was reached for the masses of 21Na and 23Mg, respectively. We reduce the uncertainty of the QEC values by a factor of 5, making them the most precise experimental input data for the calculation of the corrected Ft value of these mixed Fermi and Gamow-Teller transitions. For the 21Na→21NeQEC value, a 2.3σ deviation from the literature QEC value was found.