69Krβ-delayed proton emission: A Trojan horse for studying states in proton-unbound69Br

Abstract

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