Coupled-channel α-decay theory for odd-mass nuclei: 253Es and 255Fm

Abstract

An exact numerical coupled-channel integration treatment has been applied to the α-decay of odd-mass spheroidal nuclei. The only noncentral coupling of importance between an emitted α-particle and rotational final states in the daughter nucleus involves the intrinsic quadrupole moment of the daughter. The nuclei 253Es and 255Fm are ideal cases to examine since α-transitions to the favored bands are well known and angular distribution data from low-temperature nuclear alignment are available. We examined in detail two commonly used approximations: first, that near the nuclear surface there is zero projection of orbital angular momentum of favored α-waves along the cylindrical symmetry axis of the daughter nucleus and second, that the intensity of each α-particle l-wave is proportional to the product of a squared Clebsch-Gordan coefficient and the (calculated) spherical barrier penetrability factor. It is found that neither approximation holds within experimental error, and m l ≠ 0 α-wave components must be introduced at the nuclear surface to give agreement with experimental intensities for both l = 2 and l = 4 waves.