Lifetimes and preformation factors for the alpha-decay of the even-even actinides

Experimental lifetimes and branching ratios for the alpha-decay of even-eve n actinide nuclei can be fitted with wavefunctions at the nuclear surface w hich are practically nucleus independent. This suggests some common preform ation process across the entire mass region. Our analysis is achieved witho ut the introduction of a 'knocking frequency' and within reasonably well de fined limits, the amplitudes that we calculate can be directly related to t he alpha-particle preformation factor.