Two weakly populated rotational bands with energy spacings characteristic of superdeformation (SD) have been found in the ${}_{}{}^{186}{}_{}{}^{}\mathrm{W}$${(}^{18}$O,xn) reaction at a beam energy of E=113 MeV. One of the bands corresponds to the known sequence in ${}_{}{}^{196}{}_{}{}^{}\mathrm{Pb}$, the other to an extremely weak cascade previously assigned to ${}_{}{}^{198}{}_{}{}^{}\mathrm{Pb}$. Both bands have been extended to higher frequency. The behavior of the dynamic moments of inertia for the known SD bands in the Pb nuclei are discussed. Deformation and pairing self-consistent cranked Woods-Saxon calculations of the ${\mathit{scrI}}^{\mathrm{}\left(2\right)\mathrm{}}$ moments of inertia for Z=80 gap resulting in a slightly larger quadrupole deformation of the Pb nuclei as compared to the Hg nuclei. Thus, there seems to be a slight cancellation between increased deformation and reduced alignment, both effects being rather subtle. In very recent calculations by Satul/a and Wyss [35], it is shown that the low frequency discrepancy in ${\mathit{scrI}}^{\mathrm{}\left(2\right)\mathrm{}}$ is removed, when quadrupole pairing calculations are taken into account, the main effect originating from the ${\mathit{Y}}_{21}$ component of the quadrupole pairing interaction.

• Received 3 March 1994

DOI:https://doi.org/10.1103/PhysRevC.50.1222