High-spin states in even Hg isotopes populated in ($\alpha , \mathrm{xn}$) reactions were investigated by in-beam $\gamma$-ray and conversion electron spectroscopy. Several new excited states in the ground state band of ${}_{}{}^{198}{}_{}{}^{}\mathrm{Hg}$ and in the negative parity bands of ${}_{}{}^{198,200}{}_{}{}^{}\mathrm{Hg}$ were identified. Half-lives of a number of levels in ${}_{}{}^{194,196,198}{}_{}{}^{}\mathrm{Hg}$ were measured. In particular we obtain $T_{\frac{1}{2}}=1.38\mathrm{}\left(4\right)\mathrm{} \mathrm{and} 1.85\left(16\right)\mathrm{}$ ns for the ${12}^{+}$ and ${10}^{+}$ states in ${}_{}{}^{198}{}_{}{}^{}\mathrm{Hg}$, respectively. Intrinsic quadrupole moments $Q_0$ derived from these data and the $B(E2,0^{+}\to 2^{+})$ agree within the limits of error. These data together with the excitation energies of the ground state band are interpreted within the rotationalignment model.

NUCLEAR REACTIONS ${}_{}{}^{194,196,198}{}_{}{}^{}\mathrm{Pt}(\alpha , xn)$, $E=28, 31, 34, 48$ MeV; measured $E_{\gamma }$, $I_{\gamma }$, $\gamma \left(\theta \right)$, $\gamma \mathrm{}\left(t\right)\mathrm{}$, $\gamma \gamma$ coin, $I_{\mathrm{c}\mathrm{}\mathrm{e}}$, $\mathrm{ce}\mathrm{}\left(t\right)\mathrm{}$. ${}_{}{}^{194,196,198,200}{}_{}{}^{}\mathrm{Hg}$ deduced levels, $I$, $\pi$, $T_{\frac{1}{2}}$, ICC, $\Lambda$, $B\left(\Lambda \right)$, Rotation-alignment model.

• Received 16 August 1976

DOI:https://doi.org/10.1103/PhysRevC.15.1298