Multiple Coulomb excitation of states up to $J^{\pi }={12}^{+}$ in the ground band was measured to test the rigid-rotor prediction for intraband $B\left(E2\mathrm{}\right)\mathrm{}$ ratios. The deexcitation $\gamma$ rays were observed in singles and in the particle- $\gamma$ coincident mode following excitation by ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ or ${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}$ ions from the Oak Ridge isochronous cyclotron. $B\left(E2\mathrm{}\right)\mathrm{}$ values were extracted by comparing experimental excitation probabilities with theoretical values calculated with the Winther- de Boer computer code. An unexpected result is that the $B(E2;4\mathrm{}\to 6)$ values for ${}_{}{}^{162,164}{}_{}{}^{}\mathrm{Dy}$ are 15±5% smaller than the rotational values. However, the most striking variation of $B\left(E2\mathrm{}\right)\mathrm{}$ with spin occurs for ${}_{}{}^{160}{}_{}{}^{}\mathrm{Dy}$. We find $\frac{{B\left(E2\mathrm{}\right)\mathrm{}}_{\exp }}{{B\left(E2\mathrm{}\right)\mathrm{}}_{\mathrm{rotational}}}=0.77\mathrm{}\pm 0.05$, 0.94±0.06, and 1.29±0.14 for the 4→6, 6→8, and 8→10 transitions, respectively. The 10→8 transition in ${}_{}{}^{160}{}_{}{}^{}\mathrm{Dy}$ is significantly faster than rotational even when our approximate quantal correction of 6% is not included in the analysis.

[NUCLEAR REACTIONS ${}_{}{}^{160,162,164}{}_{}{}^{}\mathrm{Dy}$(${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}$, ${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}$′), $E=125\mathrm{}$ MeV; (${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$′), $E=72\mathrm{}$ MeV; measured Coulomb excitation yields. ${}_{}{}^{160,162,164}{}_{}{}^{}\mathrm{Dy}$ levels, deduced $E_{\gamma }$, $B\left(E2\mathrm{}\right)\mathrm{}$.]

• Received 17 September 1973

DOI:https://doi.org/10.1103/PhysRevC.9.1103