Mean Life of the 343-keV State inCd111

Abstract

The mean life of the 343-keV state in $^{111}\mathrm{Cd}$ is measured, using the delayed coincidence method, employing a $\ensuremath{\beta}\ensuremath{-}\ensuremath{\gamma}$ coincidence arrangement, with plastic crystals and the centroid shift technique. A value of 85\ifmmode\pm\else\textpm\fi{}17 psec is obtained for the mean life. This is in complete disagreement with the previous Coulomb-excitation results, and is in agreement with that of the resonance scattering experiment. The transition probabilities $T(E2)$ and $T(M1)$ are estimated, using the present value of the mean life and the available values of the conversion coefficient, mixing and branching ratios. An $E2$ enhancement of 7.5\ifmmode\pm\else\textpm\fi{}2 and $M1$ hindrance of 129\ifmmode\pm\else\textpm\fi{}33 over the single-particle estimates are noted. The theoretical values estimated using the wave functions of Kisslinger and Sorensen as well as those of Barnes are found to be unsuitable for the estimation of the transition probabilities. The experimental values are therefore employed to obtain phenomenological wave functions for the ground and the 343-keV states. The resultant wave functions show dominant ${d}_{\frac{5}{2}}$ plus phonon contributions in both the ground and the 343-keV state.