Equilibrium statistical treatment of angular momenta associated with collective modes in fission and heavy-ion reactions

First we deal with angular-momentum fractionation along the mass asymmetry co-ordinate. As this degree of freedom is the slowest to equilibrate, this section is perhaps more relevant to fission than to deep inelastic processes. Yet there exists, in heavy-ion reactions, components which are apparently equilibrated along the mass asymmetry mode and yet are difficult to explain by compound-nucleus decay. It is possible that our formalism may enable one to learn about these components as well. In the second part we treat the equilibrium partition of angular momentum between orbital and intrinsic rotation which involves the excitation of the collective modes known as wriggling. The effect of the wriggling mode on the fragment spin alignment is discussed. We then allow the disintegration axis to tilt with respect to the plane normal to the total angular momentum. The average fragment angular momentum is obtained and the spin and angular fluctuations are estimated. The thermal excitation of twisting and bending modes is studied for a system with zero and finite total angular momentum. The first and second moment of the fragment angular momentum as well as the fragment angular-momentum depolarization are evaluated. Finally, the results so obtained are applied to the reaction 600 MeV Kr+Au, and numerical estimates of angular momenta and their alignment are calculated. (orig./HSI)