Low-spin states of ${}_{}{}^{250}{}_{}{}^{}\mathrm{Cf}$ have been investigated by measuring $\gamma$ rays and conversion electrons associated with the electron capture decay of 2.22-h ${}_{}{}^{250}{}_{}{}^{}\mathrm{Es}$. Mass-separated ${}_{}{}^{250}{}_{}{}^{}\mathrm{Es}$ samples produced by the ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}(d, n)$ reaction were used for these measurements. The $\gamma$-ray spectra were measured with a 25-${\mathrm{cm}}^3$ coaxial Ge(Li) spectrometer and the electron spectra were measured with a cooled Si(Li) detector. Multipolarities of intense transitions in ${}_{}{}^{250}{}_{}{}^{}\mathrm{Cf}$ were deduced and $log\mathrm{ft}$ values of electron capture transitions were derived from measured electron capture intensities. On the basis of the results of the present investigation the following bandheads were identified in ${}_{}{}^{250}{}_{}{}^{}\mathrm{Cf}$: $E$ (keV),$K$, $I\pi =871.6, 2, 2-; 1031.9, 2, 2+; 1154.2, 0, 0+; 1175.5, 1, 1-; 1210.0, 2, 2-; 1244.4, 2, 2+; 1266.5, 0, 0+; \mathrm{and} 1658.1, 2, 2+$. The 2.22-h state in ${}_{}{}^{250}{}_{}{}^{}\mathrm{Es}$ has been given a spin-parity assignment of 1- with configuration ${\mathrm{}\left\{n\right[734\mathrm{}]\mathrm{}\frac{9}{2-}; p[633\left]\mathrm{}\frac{7}{2+}\right\}}_{1-}$.

RADIOACTIVITY ${}_{}{}^{250}{}_{}{}^{}\mathrm{Es}$ [from ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}(d, n)$]; measured $T_{\frac{1}{2}}$, $E_{\gamma }$, $I_{\gamma }$, $E_{\mathrm{ce}}$, $I_{\mathrm{ce}}$. ${}_{}{}^{250}{}_{}{}^{}\mathrm{Cf}$ deduced levels, $log\mathrm{ft}$ (EC), $\gamma$ multipolarity, $I$, $\pi$. Mass-separated ${}_{}{}^{250}{}_{}{}^{}\mathrm{Es}$. Cooled Si(Li) electron spectrometer.

• Received 28 December 1979

DOI:https://doi.org/10.1103/PhysRevC.22.1226