β-delayed proton decays of the nuclides ${}_{}{}^{27}{}_{}{}^{}\mathrm{P}$ and ${}_{}{}^{31}{}_{}{}^{}\mathrm{Cl}$ were measured using the helium-jet recoil collection technique and low-energy particle identification detector telescopes. In ${}_{}{}^{27}{}_{}{}^{}\mathrm{P}$, two new proton groups at 466±3 keV and 612±2 keV, with intensities of 9±2% and 97±3% relative to the main (100%) group at 731±2 keV, were discovered. Additionally, during the ${}_{}{}^{27}{}_{}{}^{}\mathrm{P}$ experiments, a new proton transition was identified following the β decay of ${}_{}{}^{28}{}_{}{}^{}\mathrm{P}$. This group, at a proton energy of 1452±4 keV, had a 2±1% intensity relative to the 100% group at 679±1 keV. A total ${}_{}{}^{27}{}_{}{}^{}\mathrm{P}$ β-delayed proton branch of 0.07% was estimated. The experimental Gamow-Teller β-decay strengths of the observed transitions from ${}_{}{}^{27}{}_{}{}^{}\mathrm{P}$ were compared to results from shell model calculations. A search for new proton transitions in ${}_{}{}^{31}{}_{}{}^{}\mathrm{Cl}$, the next member of this A=4n+3, ${\mathit{T}}_{\mathit{z}}$=-3/2 series, was unsuccessful. However, several proton peaks that had been previously assigned to ${}_{}{}^{31}{}_{}{}^{}\mathrm{Cl}$ decay were shown to be from the decay of ${}_{}{}^{25}{}_{}{}^{}\mathrm{Si}$. © 1996 The American Physical Society.

• Received 20 May 1996

DOI:https://doi.org/10.1103/PhysRevC.54.1098