α-particle preformation for favoured transitions using proximity potential

Abstract

α-particle preformation probability (P0) is calculated for favoured transitions of all α-emitters. An indirect approach is employed in which P0 is given by the ratio of the experimental values of α-decay constant and theoretically determined values of assault frequency and the penetrability. The proximity potential is used for determination of the penetrability, and the assault frequency is calculated through a modified formula. Analysis of the results show that P0 is highest for the even–even type, and lowest for the odd–odd type α-emitter. Also, it is noted that P0 is higher for transitions originating in the ground state, and lower for transitions originating in the isomeric state. This suggests that there is greater preformation of α-particle in the ground state than in the isomeric state. P0 values show a distinct minima at the neutron magic number, N = 126. Also, it is noted that values of α-decay fraction (fα) reported in the literature for a few α-emitters are, either, not consistent, or only limiting values are available. This raises the possibility of determining improved values of P0 if accurate values of fα are known in future.