Fission Before K Statistical Equilibration

For the reaction systems with α < α_BG, the fissioning nucleus goes through saddle-point to fission with some memories of the entrance-channel plane. In these cases, by taking the relaxation process of K degree of freedom into account, the varience of K distribution, σ²_k is obtained. It is shown that σ²_k exponentially depends on the square of the angular momentum, J² for the reaction systems with α < α_BG.Therefore, we have put forward a new version of preequilibrium fission model, and shown the experimental evidence for this new fission mechanism.