Lifetime and Multipolarity Measurements inCs131

With the use of the Berkeley $\surd 2\pi$, iron-free, beta-ray spectrometer, the half-life of the 78.69-keV state in ${\mathrm{Cs}}^{131}$ has been measured as (9.6±0.3) nsec, and that of the 133.54-keV state has been redetermined as (9.3±0.3) nsec. An upper limit of ≤0.4 nsec has been found for the half-life of the 216.01-keV state. $L$-subshell ratios, and multipolarity assignments based thereon, are given for a number of transitions in ${\mathrm{Cs}}^{131}$. A new transition with an energy of 969.1 keV has been observed, and the 461-keV transition was found to consist of a doublet with energies of 461.3 and 462.9 keV. The data indicate that the ground ($\frac{5}{2}+$) and 78.69-keV ($\frac{7}{2}+$) states of ${\mathrm{Cs}}^{131}$ probably arise from different intrinsic states ($d_{\frac{5}{2}}$ and $g_{\frac{7}{2}}$, respectively) upon which are based collective levels located at 123.73 and 133.54 keV. Tentative spin and parity assignments are included. Poor agreement is found with existing theoretical predictions.