In this study the decay of ${}_{}{}^{149}{}_{}{}^{}\mathrm{Er}_{}^{\mathrm{g}+\mathrm{m}}{}_{}{}^{}$ by positron emission, electron capture, and β-delayed proton emission was investigated. Gamma rays associated with ${}_{}{}^{149}{}_{}{}^{}\mathrm{Er}_{}^{\mathrm{m}}{}_{}{}^{}$ decay were placed in a decay scheme on the basis of γγ and xγ coincidences and half-life. We assigned 120 γ rays deexciting 91 levels in ${}_{}{}^{149}{}_{}{}^{}\mathrm{Ho}$ to 8.9±0.2 s ${}_{}{}^{149}{}_{}{}^{}\mathrm{Er}_{}^{\mathrm{m}}{}_{}{}^{}$ decay. The π$s_{1/2}$ single-particle state in ${}_{}{}^{149}{}_{}{}^{}\mathrm{Ho}$ was observed to occur at 49.0 keV above the π$h_{11/2}$ ground state. A (3.5±0.7) % isomeric transition decay branch and a (0.18±0.07) % β-delayed proton decay branch were determined for ${}_{}{}^{149}{}_{}{}^{}\mathrm{Er}_{}^{\mathrm{m}}{}_{}{}^{}$ decay. Three additional γ rays were assigned to 4±2 s ${}_{}{}^{149}{}_{}{}^{}\mathrm{Er}_{}^{\mathrm{g}}{}_{}{}^{}$ decay and a (7±2) % β-delayed proton decay branch was determined. Measured EC/${\beta }^{+}$ ratios to proton emitting states in ${}_{}{}^{149}{}_{}{}^{}\mathrm{Ho}$ resulted in a (${\mathit{Q}}_{\mathit{EC}}$-${\mathit{S}}_{\mathit{p}}$)=7.$0_{\mathrm{-}0.4}^{+5.0\mathrm{}}$ MeV for ${}_{}{}^{149}{}_{}{}^{}\mathrm{ER}_{}^8{}_{}{}^{}$ decay and a ${\mathit{S}}_{\mathit{p}}$=1.$4_{\mathrm{-}0.6}^{+10\mathrm{}}$ MeV for Ho. The β-delayed proton spectrum from ${}_{}{}^{149}{}_{}{}^{}\mathrm{Er}_{}^{\mathrm{g}}{}_{}{}^{}$ consisted of a highly structured component corresponding to the deexcitation of levels between 4 and 5 MeV in ${}_{}{}^{149}{}_{}{}^{}\mathrm{Ho}$ and a structureless component corresponding to decay from higher levels. The β-strength function for ${}_{}{}^{149}{}_{}{}^{}\mathrm{Er}_{}^{\mathrm{g}+\mathrm{m}}{}_{}{}^{}$ decay is discussed in terms of single-particle shell-model structure, weak coupling to the ${}_{}{}^{148}{}_{}{}^{}\mathrm{Dy}$ core, and decay of π$h_{11/2}$ protons across the shell closure to the ν$h_{9/2}$ neutron orbital.

• Received 6 July 1988

DOI:https://doi.org/10.1103/PhysRevC.39.219