A comparison of the penetrabilities calculated in the Wentzel-Kramers-Brillouin approximation through equivalent multihumped fission barriers shows that the penetrability saturates to its maximum value much more slowly for a three-humped potential than that for comparable two-humped and single-humped potentials. An analysis of the slopes of the near-barrier photofission cross sections of actinides yields results that can be understood in terms of the predicted potential barrier shapes for these nuclei, and thus provides evidence in support of resolving the ‘‘thorium anomaly’’ along the lines suggested by Möller and Nix. Our results further indicate that the uranium nuclei, and in particular ${}_{}{}^{236}{}_{}{}^{}\mathrm{U}$, may more likely exhibit three-humped potential shapes in which the apparent consequences of both the second and third minima may be observable.

• Received 17 March 1988

DOI:https://doi.org/10.1103/PhysRevC.39.917