Emergence of rotational modes in nuclear fission

Abstract

Dinuclear systems that occur in the post-saddle to scission stage in nuclear fission process are special transient formations. The diabatic evolution at this stage is studied using the methods of non-equilibrium thermodynamics. A novel explanation for the emergence of intrinsic rotational modes that occur in such a dinucleus is developed by identifying these modes together as an open subsystem that exchanges matter and energy with its environment. The environment consists of all remaining degrees of freedom of the dinucleus, and a weak coupling of the subsystem to this environment facilitates a diabatic energy exchange. Under appropriate non-equilibrium conditions, the available energy is coupled to the work needed for the emergence of self organizing rotational modes. This comes at the expense of increasing microscopic disorder in the form of intrinsic excitations in the prefragments. A simple formalism is presented such that the magnitudes of relevant energy flow through the subsystem are obtained in terms of entropy production rate, entropy expulsion rate and net rate of change of entropy in sub-units of $MeV zs^{-1} K^{-1}$.