Identification of the Lowest T=2, Jπ=0+ Isobaric Analog State in 52Co and Its Impact on the Understanding of β-Decay Properties of 52Ni

Masses of Co-52g,Co-52m were measured for the first time with an accuracy of similar to 10 keV, an unprecedented precision reached for short-lived nuclei in the isochronous mass spectrometry. Combining our results with the previous beta-gamma measurements of Ni-52, the T = 2, J(pi) = 0(+) isobaric analog state ( IAS) in Co-52 was newly assigned, questioning the conventional identification of IASs from the beta-delayed proton emissions. Using our energy of the IAS in Co-52, the masses of the T = 2 multiplet fit well into the isobaric multiplet mass equation. We find that the IAS in Co-52 decays predominantly via gamma transitions while the proton emission is negligibly small. According to our large-scale shell model calculations, this phenomenon has been interpreted to be due to very low isospin mixing in the IAS.