69 Kr β -delayed proton emission: A Trojan horse for studying states in proton-unbound 69 Br

Particle decay of 69Br and 65As was observed through β-delayed proton emission of 69Kr and 65Se, respectively. Decay spectroscopy was performed through β-p correlations using a position-sensitive silicon-implantation detector surrounded by a γ -ray detector array. A β-decay half-life of 27(3) ms was measured for 69Kr and 33(4) ms for 65Se. The 69Kr ground state decays by a superallowed transition to its unbound isobaric analog state in 69Br which immediately decays by a 2.97(5)-MeV proton group to the first excited state in 68Se at 854.2 keV. This chain of decays constrains both the mass and spin of the 69Kr ground state. We observed no evidence of ground-state proton decay from 69Br.