Angular distributions of prompt γ-rays in the binary and the light charged particle accompanied fission modes of 252Cf

Double-differential emission probabilities Wγ(Θγ,LF, Eγ) in angle Θγ,LF and energy Eγ for prompt γ-rays have been measured in the spontaneous fission of 252Cf. The detector system allowed the γ-deexcitation in both the binary and the light charged particle accompanied fission modes to be studied under equal conditions. Previous results for the binary fission mode have been confirmed. For the first time anisotropic γ-angular distributions were proved for the light charged particle accompanied fission mode. The γ-anisotropies are rather similar for both fission modes but the shapes of the angular distributions differ considerably. The γ-deexcitation of the fission fragments in the yrast region was described on the basis of the VMI model whereas reasonable assumptions were made for statistical γ-emission. A simulation procedure starts from this conception and it was possible to reproduce γ-ray spectra and the corresponding γ-angular distributions. The observed energy-dependent shift of the maximum in the light charged particle accompanied fission mode may be understood as an influence of the equatorial alpha particles on the alignment of angular momentum produced in bending modes. (orig.)