Decay ofGdm+g143by positron emission and electron capture

In this study the decay of ${}_{}{}^{143}{}_{}{}^{}\mathrm{Gd}_{}^{g+m}{}_{}{}^{}$ by positron emission and electron capture and the isomeric decay of ${}_{}{}^{143}{}_{}{}^{}\mathrm{Eu}_{}^m{}_{}{}^{}$ were investigated. $\gamma$ rays associated with ${}_{}{}^{143}{}_{}{}^{}\mathrm{Gd}_{}^{g+m}{}_{}{}^{}$ were placed on the basis of excitation functions, half-life, and $\gamma -\gamma$ coincidence information. We assigned 61 $\gamma$ rays deexciting 33 levels in ${}_{}{}^{143}{}_{}{}^{}\mathrm{Eu}$ from the decay of 112±2 sec ${}_{}{}^{143}{}_{}{}^{}\mathrm{Gd}_{}^m{}_{}{}^{}$. Another 7 $\gamma$ rays deexcite an additional 6 levels in ${}_{}{}^{143}{}_{}{}^{}\mathrm{Eu}$ from 39±2 sec ${}_{}{}^{143}{}_{}{}^{}\mathrm{Gd}_{}^g{}_{}{}^{}$ decay. A small delayed $p$ or $\alpha$ branch associated with ${}_{}{}^{143}{}_{}{}^{}\mathrm{Gd}$ decay was observed with an upper limit of 1 × ${10}^{-5\mathrm{}}$. The half-life of the ${}_{}{}^{143}{}_{}{}^{}\mathrm{Eu}_{}^m{}_{}{}^{}$ isomer at 389.47 keV was found to be 50.0±0.5 μ sec. The resulting level structure observed in ${}_{}{}^{143}{}_{}{}^{}\mathrm{Eu}$ is explained quite satisfactorily in terms of a triaxial weak-coupling model.