Fission-fragment angular distributions in a number of heavy-ion-induced fusion reactions are explained on the basis that for composite systems with fission barrier heights comparable to their intrinsic temperatures, a fraction of the fission events take place before the fused system equilibrates fully in the $K$ degree of freedom. A value of about 8×${10}^{-21\mathrm{}}$ s is deduced for the characteristic time for $K$ equilibration.

• Received 7 June 1984

DOI:https://doi.org/10.1103/PhysRevLett.54.178