$E0\mathrm{}$ transitions identified in ${}_{}{}^{250}{}_{}{}^{}\mathrm{Cf}$ establish two excited $0^{+}$ states at 1154.2 and 1266.5 keV with dimensionless ratios $X$ of 0.27 ± 0.03 and 2.5 ± 0.3, respectively. This is the heaviest nucleus in which excited $0^{+}$ states have been observed. Using density-dependent pairing matrix elements and appropriate single-particle energies we have calculated the energies of seniority 0 $K\pi =0^{+}$ excited states to be 1310 and 1620 keV and the energy of the lowest $s=2\mathrm{}$ $0^{+}$ state as 1430 keV. These calculations suggest that the 1154.2 keV state is probably the lowest pair vibration and the 1266.5 keV state is possibly the lowest $s=2\mathrm{}$ $0^{+}$ state.

RADIOACTIVITY ${}_{}{}^{250}{}_{}{}^{}\mathrm{Es}$ [from ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}$($d$,$n$)]; measured $E_{\gamma }$, $I_{\gamma }$, $E_{\mathrm{ce}}$, $I_{\mathrm{ce}}$. ${}_{}{}^{250}{}_{}{}^{}\mathrm{Cf}$ deduced levels, $log\mathrm{ft} \mathrm{}\left(\mathrm{EC}\right)\mathrm{}$, $\gamma$ multipolarity, $I$, $\pi$, Two excited $0^{+}$ states. Mass-separated ${}_{}{}^{250}{}_{}{}^{}\mathrm{Es}$.

• Received 6 November 1978

DOI:https://doi.org/10.1103/PhysRevC.19.1140