K-forbidden allowed $ \beta$ transitions in heavy nuclei.

The role of the band quantum number K in influencing the character of allowed $ \beta$ transitions in heavy deformed nuclei is examined. The conditions for the occurrence of K -forbidden decays in this region are explored. Specific cases of “allowed” $ \beta$ decays proceeding via $ \Delta$ K = 2 to $ \Delta$ K = 6 channels are presented to illustrate the phenomenon. The listed $ \Delta$ K = 2 transitions, which by themselves contribute over 10% of all the presently known allowed transitions for A $ \geq$ 228 nuclei, are seen to have an average $\ensuremath\log ft \geq 9.0$ , which is clearly outside the normal range for allowed transitions. It is concluded that, wherever the $ \beta$ -connected states can be confidently labelled using the $\ensuremath I^{\pi}K$ quantum numbers, the K -forbiddenness is in general as significant as that involving the other two (spin and parity) quantum numbers. [ABSTRACT FROM AUTHOR]