α-particle decay through a deformed barrier

The eigenchannel formalism of sub-barrier fusion is extended to the α-decay of even-even nuclei. Despite an enormous advantage attainable by transmission through the maximum-flux eigenchannel, corresponding to penetration through the low barrier polar region of the deformed prolate daughter, branching ratios suggest that deformed actinide nuclei take a different decay path imposed by the preformed angular momentum superposition in the nuclear interior. Using both WKB and coupled-channels transmission matrices, we have found that all known branching ratios of even-even actinide nuclei can be fitted with essentially the same internal amplitudes. Under the assumption that daughter states do not mix during barrier penetration, these same amplitudes also give good results for the known anisotropies of favoured decays and the branching ratios of odd nuclei in the same mass region.