The beta-delayed proton decay of 23Al

Aluminum-23 was produced in two 40 MeV proton bombardments of Mg targets at LBNL’s 88-Inch Cyclotron. Reaction products were transported by helium jet to a detection chamber. They were observed by two low-energy particle-identification telescopes; each consisted of two gas-ΔE detectors, a thin (<70 μm) Si E detector and a 300 μm Si E-reject detector. Contrary to previous measurements, the lowest energy peak in the spectrum was observed at an energy of 246±20 keV with 33±3% of the intensity of the peak at 838±5 keV. Implications for isospin mixing and the proton-capture width of the 23Al isobaric analog state in 23Mg are discussed. Other weak beta-delayed proton-decay branches were also observed with energies up to ∼2200 keV.