Two-proton decay of 12O and its isobaric analog state in 12N

摘要

Following neutron knockout from an 13O beam, 12O fragments were created and the three decay productsnfollowing two-proton decay were detected. A new ground-state mass was determined by the invariant massnmethod implying a decay kinetic energy of 1.638(24) MeV, and the width was found to be less than 72 keV.nThe latter is inconsistent with previous measurements with lower experimental resolutions but consistent withntheoretical estimates. The isobaric analog of 12O in 12N was produced from proton knockout reactions with thensame beam and decayed by two-proton emission to the isobaric analog state in 10B with a decay kinetic energy ofn1.165(29) MeV. It represents only the second case of an analog state where two-proton decay is the only isospinandnenergy-conserving particle decay mode. With our measurements of the mass excesses of 12O and its analog,nthe quadratic form of the isobaric multiplet mass equation was found to fit the A = 12 quintet and any deviationsnare less than the magnitude found for the A = 8 quintet and A = 7 and 9 quartets.