Two isomers with $K^{\pi }=19/2^{+}$ at 1876 keV with a half-life of 21(1) ns, and $K^{\pi }=23/2^{-}$ at 2159 keV with a half-life of 93(6) ns have been identified in ${}^{173}\mathrm{W}$, the lightest tungsten isotope to exhibit this phenomenon. An unusually high number of 13 branches have been established in the decay of the $K^{\pi }=23/2^{-}$ isomer. This decay is associated with transitions involving significantly higher degrees of $K$ forbiddenness and is in sharp contrast with the usual preferential deexcitation through branches, which are less forbidden, as is evident for the $K^{\pi }=19/2^{+}$ state in ${}^{173}\mathrm{W}$. The inclusion of $K$-mixing effects, arising from band crossings in the sequences to which decays with larger degrees of $K$ forbiddenness are observed, can qualitatively account for this contrasting behavior. These results provide a striking illustration of the competition between $K$ conservation and $K$ mixing in the decay of such isomers.

Close

PrevNext

View figure in article

• High spin states
• Isomer decays
• Lifetimes & widths
• Nuclear structure & decays
• 150 ≤ A ≤ 189
• Collective models