Yrast superdeformed band in194Pb:JπandEx

Abstract

The yrast superdeformed band in ${}^{194}$Pb has been populated using the ${}^{174}$Yb${(}^{25}$Mg,5n)${}^{194}$Pb reaction at $E_{\mathrm{beam}}=130\mathrm{}$ MeV. Decay $\gamma$ rays were detected using the GAMMASPHERE array at the 88-Inch Cyclotron. Twelve $\gamma$-ray transitions have been observed directly linking three members of the ${}^{194}$Pb yrast superdeformed band to low-lying normal deformed levels. Anisotropy measurements indicate that these linking decays include $E$1, $M$1, and mixed $M1/E2\mathrm{}$ multipolarities. The radiative widths deduced are very inhibited, typically $B\left(E1\mathrm{}\right)\mathrm{}\sim {10}^{-8}$ Weisskopf units (W.u.) and $B\left(M1\mathrm{}\right)\mathrm{}\sim {10}^{-5}$ W.u. Without recourse to a priori assumptions $J^{\pi }{=6\mathrm{}}^{+}$ and $E_x=4878.4\mathrm{}\left(3\right)\mathrm{}$ keV have been unambiguously assigned to the lowest-lying observed superdeformed state (the state populated by the 170-keV intraband transition). The intensity of the observed primaries accounts for 21(2)% of the superdeformed band population.