Lifetime measurements in the ${10}^{-9\mathrm{}}$ sec range have been made for $E2\mathrm{}$ or $M1+E2\mathrm{}$ transitions in the following nuclei: ${\mathrm{Sm}}^{152}$, ${\mathrm{Gd}}^{154}$, ${\mathrm{Hf}}^{180}$, ${\mathrm{W}}^{182}$, ${\mathrm{Os}}^{188}$, ${\mathrm{Ir}}^{191}$, ${\mathrm{Au}}^{197}$, and ${\mathrm{Po}}^{210}$. Upper limits for lifetimes have been established for $E2\mathrm{}$ or $M1+E2\mathrm{}$ transitions in ${\mathrm{Ir}}^{191}$, ${\mathrm{Pb}}^{204}$, ${\mathrm{Pb}}^{206}$, ${\mathrm{Pb}}^{207}$, and ${\mathrm{U}}^{234}$. $E2\mathrm{}$ radiative transition probabilities are considered within the framework of the Bohr-Mottelson unified nuclear model. For neutron number $N=90-126\mathrm{}$, distortion parameters evaluated from $E2\mathrm{}$ radiative lifetimes are about 5-6 times smaller than those evaluated from first excited state energies of even-even nuclei.

• Received 11 January 1955

DOI:https://doi.org/10.1103/PhysRev.98.653