Unfavored Factors for AllowedβTransitions

Unfavored factors $U$, that is, ratios of computed-to-observed transition probabilities, are tabulated in a systematic manner for allowed $\beta$ transitions in the strict $j-j$ coupling scheme. The introduction of many-particle wave functions lowers the gap between favored and unfavored transitions, but does not eliminate it. The systematics brings out clearly the role of configuration interaction through a strong correlation between the $U$ factors and the expected purity of the shell-model wave functions. The matrix elements for even-$A$ nuclei are on the average larger than those for odd-$A$ nuclei and thus explain without any new hypothesis the lower average $\mathrm{ft}$ values for the even-$A$ group.