Alpha decay and nuclear deformation: the case for favoured alpha transitions of even-even emitters

Alpha decay half-life for ground-state to ground-state transitions of 174 e ven-even alpha emitters has been calculated from a simple, Gamow-like model in which the quadrupole deformation of the product nucleus (assumed to hav e an ellipsoidal shape) is taken into account. The assumption made is that before tunnelling through a purely Coulomb potential barrier the two-body s ystem oscillates isotropically, thus giving rise to an equivalent, average polar direction Bo (referred to the symmetry axis of the ellipsoid) for alp ha emission. It is shown that the experimental half-life data are much bett er reproduced by the present description than in the spherical shaped appro ximation for the daughter nucleus.