A preliminary report on the discovery of isomeric states in ${}_{}{}^{250}{}_{}{}^{}\mathrm{Fm}$ and ${}_{}{}^{254}{}_{}{}^{}\mathrm{No}$ was included in a recent article on $\alpha$-emitting isotopes of element 104. The existence and assignments of the 1.8 ± 0.1-sec isomer to ${}_{}{}^{250}{}_{}{}^{}\mathrm{Fm}$ and the 0.28 ± 0.04-sec isomer to ${}_{}{}^{254}{}_{}{}^{}\mathrm{No}$ have now been confirmed by cross-bombardment techniques. Isomeric ratios based on measurements of collection efficiency of recoil atoms from the decay of isomeric states are given. An interpretation of the even-even isomers as high-spin two-quasiparticle states is discussed.

• Received 30 November 1972

DOI:https://doi.org/10.1103/PhysRevC.7.2032