The level mixing spectroscopy method has been applied to measure the static quadrupole moments of six isomeric states in ${}_{}{}^{213}{}_{}{}^{}\mathrm{Fr}$, ${}_{}{}^{212}{}_{}{}^{}\mathrm{Fr}$, and ${}_{}{}^{211}{}_{}{}^{}\mathrm{Fr}$ (Z=87). For isomers with the proton configuration π${\mathit{h}}_{9/2}^4$${\mathit{i}}_{13/2}$ a large increase of the quadrupole moment was observed with the removal of neutrons from the closed N=126 core: Q(29/$2^{+}$${,}^{213}$Fr)=-70(7) e ${\mathrm{fm}}^2$, Q(${15}^{\mathrm{-}}$${,}^{212}$Fr)=-80(12) e ${\mathrm{fm}}^2$, and Q(29/$2^{+}$${,}^{211}$Fr)=-107(18) e ${\mathrm{fm}}^2$. Quadrupole moments for very high spin states were also measured: Q(65/$2^{\mathrm{-}}$${,}^{213}$Fr)=-219(53) e ${\mathrm{fm}}^2$, Q(${27}^{\mathrm{-}}$${,}^{212}$Fr)=-152(31) e ${\mathrm{fm}}^2$, and Q(45/$2^{\mathrm{-}}$${,}^{211}$Fr) =-198(56) e ${\mathrm{fm}}^2$. The observed values are in good agreement with shell-model calculations, but are lower than that predicted using the deformed-independent particle model. The implantation behavior of Fr in a Tl host is also discussed.

• Received 20 June 1990

DOI:https://doi.org/10.1103/PhysRevC.43.514