The half-lives of the 99.1-keV level in ${\mathrm{Dy}}^{158}$ and the 79.6-keV level in ${\mathrm{Gd}}^{158}$ have been measured to be 1.64±0.08 nsec and 2.47±0.10 nsec, respectively, using a source of ${\mathrm{Tb}}^{158}$ (150 yr) and a time-to-amplitude converter circuit. In addition, the following half-lives were measured: 86.8-keV state in ${\mathrm{Dy}}^{160}$, 2.02±0.09 nsec; 84.2-keV state in ${\mathrm{Yb}}^{170}$, 1.56±0.08 nsec; 76.5-keV state in ${\mathrm{Yb}}^{174}$, 1.74±0.09 nsec; 100.1-keV state in ${\mathrm{W}}^{182}$, 1.35±0.7 nsec; 1289-keV state in ${\mathrm{W}}^{182}$, 1.06±0.05 nsec. A compilation of the more recent data on first excited state half-lives, $B\left(E2\mathrm{}\right)\mathrm{}$ values, and deformation parameters is presented for the even-even rotational nuclei in the region $Z=60-68\mathrm{}$. A comparison is made between values determined from half-life and Coulomb-excitation measurements.

• Received 20 August 1965

DOI:https://doi.org/10.1103/PhysRev.141.1200