Mass dependence of fragment anisotropy in the fission of 11B+237Np and 16O+209Bi systems

Measurements were carried out on mass, energy correlations of fission fragments for the systems of 11B+237Np at Elab=76 MeV and 16O+209Bi at Elab=100 MeV at forward and perpendicular angles of emission with respect to the beam direction. The fragment anisotropy averaged over all fragment masses matches well for both the systems with the standard saddle point statistical model calculations. Variation of the angular anisotropy and total kinetic energy of fragments were studied as a function of the mass of the fragment pair. For the 11B+237Np system, the fragment anisotropy is seen to be nearly independent of the fragment mass, whereas for the 16O+209Bi system, the anisotropy is seen to decrease with increasing fragment mass asymmetry. The results are discussed on the basis of the statistical model of fragment angular distributions and mass division in the fission process. copyright 1996 The American Physical Society