High-precision QEC values of superallowed 0+ → 0+β-emitters 46Cr, 50Fe and 54Ni

Abstract Short-lived 46 Cr, 50 Fe and 54 Ni were studied by isochronous mass spectrometry at the HIRFL-CSR facility in Lanzhou. The measured precision mass excesses ( M E ) of 46 Cr, 50 Fe and 54 Ni are − 29471 ( 11 )  keV , − 34477 ( 6 )  keV and − 39278 ( 4 )  keV , respectively. The superallowed 0 + → 0 + β -decay Q values were derived to be Q EC ( Cr 46 ) = 7604 ( 11 )  keV , Q EC ( Fe 50 ) = 8150 ( 6 )  keV and Q EC ( Ni 54 ) = 8731 ( 4 )  keV . The values for 50 Fe and 54 Ni are by one order of magnitude more precise than the adopted literature values. By combining the existing half-lives and branching ratios, we obtained the corrected F t values to be F t ( Fe 50 ) = 3103 ( 70 )  s and F t ( Ni 54 ) = 3076 ( 50 )  s . The main contribution to the F t uncertainties is now due to β -decay branching ratios, still, more high-precision measurements of the half-lives, the masses, and especially the branching ratios are needed in order to satisfy the requirements for a stringent CVC test.