The β-delayed γ and proton decay of 23 Al has been studied with a novel detector setup at the focal plane of the MARS separator at Texas A&M University. We could detect protons down to an energy of 200 keV and determine the corresponding branching ratios. Contrary to results of previous β-decay studies, no strong proton intensity from the decay of the isobaric analog state (IAS) of the 23 Al ground state at Ex = 7803 keV in 23 Mg, was observed. Instead we assign the observed low energy group Ep,cm = 206 keV to the decay from a state 16 keV below the IAS. We measured both proton and gamma branches from the decay of this state at Ex = 7787 keV in 23 Mg, a very rare case in the literature. Combining our data with its measured lifetime, we determine its resonance strength to be ωγ = 1.4 +0.5 −0.4 meV. The value is in agreement with older direct measurements, but disagrees with a new direct measurement. This state is the most important resonance for the radiative proton capture 22 Na(p,γ) 23 Mg in some astrophysical environments, such as novae.

Following neutron knockout from a 13 O beam, 12 O fragments were created and the three decay products following two-proton decay were detected. A new ground-state mass was determined by the invariant mass method implying a decay kinetic energy of 1.638(24) MeV, and the width was found to be less than 72 keV. The latter is inconsistent with previous measurements with lower experimental resolutions, but consistent with theoretical estimates. The isobaric analog of 12 O in 12 N was produced from proton knockout reactions with the same beam and decayed by twoproton emission to the isobaric analog state in 10 B with a decay kinetic energy of 1.165(29) MeV. It represents only the second case of an analog state where two-proton decay is the only isospin and energy conserving particle decay mode. With our measurements of the mass excesses of 12 O and it analog, the quadratic form of the isobaric multiplet mass equation was found to fit the A=12 quintet and any deviations are less than the magnitude found for the A=8 quintet and A=7 and 9 quartets.

We report the first branching-ratio measurement of the superallowed 0+→0+β transition from Ca38. The result, 0.7728(16), leads to an ft value of 3062.3(68) s with a relative precision of ±0.2%. This makes possible a high-precision comparison of the ft values for the mirror superallowed transitions, Ca38→38mK and K38m→Ar38, which sensitively tests the isospin symmetry-breaking corrections required to extract Vud, the up-down quark-mixing element of the Cabibbo-Kobayashi-Maskawa (CKM) matrix, from superallowed β decay. The result supports the corrections currently used and points the way to even tighter constraints on CKM unitarity.

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