POSSIBLE CLUSTER PREFORMATION IN THE C-14 DECAY OF RA-223

A recent experiment on the C14 fine structure has shown that the branching ratio to Pb209 ground state is quite different from the one predicted by the various models of cluster emission. Assuming that the C14 is preformed in the Ra223 nucleus, we have calculated the hindrance factor F14C of the three C14 branches to Pb209 states with a barrier penetrability approximated by a square-well Coulomb potential. The F14C=3.9 and 4.6 values found for the C14 transitions to the two excited states at 779 keV (I=11/2+) and 1423 keV (I=15/2-), respectively, reveal that the cluster formation amplitudes in both transitions are close to those of the Ra222 and Ra224 C14 decays. Such values could be the result of -nlj shell-model components common to both the wave functions of the octupole deformed Ra223 nucleus and of the two first excited states of Pb209 spherical nucleus. The high hindrance factor F14C=583 of the C14 branch to the Pb209 ground state (I=9/2+) could reveal the absence of -1g9/2 shell-model component in the Ra223 wave function. © 1990 The American Physical Society.