Structure ofRu108,110,112: Identical bands inRu108,110

The levels ${\mathrm{in}}^{108,110,112}$Ru have been investigated in the spontaneous fission of ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$ using γ-γ-γ-, γ-γ-, x-x-, x-γ-, and x-γ-γ-coincidence techniques. The levels up to ${16}^{+}$ and $9^{+}$ in the yrast bands and γ-vibrational bands have been identified with very little energy staggering in ${}_{}{}^{108,110,112}{}_{}{}^{}\mathrm{Ru}$. The ground bands in ${}_{}{}^{108,110}{}_{}{}^{}\mathrm{Ru}$ have identical γ-ray transition energies up to $8^{+}$. These are the lightest observed even-even nuclei with extended identical ground bands. Calculations in a collective model which includes rotations and vibrations reproduce the level energies and γ band branching ratios above the $3^{+}$ state rather well, while rigid triaxial rotor model calculations reproduce the branching ratios for the $2^{+}$ and $3^{+}$ states.