Asymmetry in the super-allowed $\beta$-transitions of the A=9 isobars

We report here on the recent $\beta$-decay studies of the A = 9 isobar made at ISOLDE/CERN. Mirror $\beta$ - transitions in the A=9 chain are compared and a large asymmetry factor is deduced for the transitions to high excitation energy in $^{9}$Be (11.8 MeV) and $^{9}$B (12.2 MeV) fed in the $\beta$-decay of $^{9}$Li and $^{9}$C respectively. It is shown that the asymmetry is not due to experimental problems or differences in the mechanisms of breakup or in the spin of the states. Only differences in the partial decay branches of the breakup channels have been found. As no asymmetry is found in the gs to gs transition it must be due to the particular structure of these excited states. (14 refs).