Reaction initial state.

The Geant4 precompound model is considered as an extension of the hadron kinetic model. It gives a possibility to extend the low energy range of the hadron kinetic model for nucleon-nucleus inelastic collision and it provides a “smooth” transition from kinetic stage of reaction described by the hadron kinetic model to the equilibrium stage of reaction described by the equilibrium deexcitation models.

The initial information for calculation of pre-compound nuclear stage consists from the atomic mass number \(A\), charge \(Z\) of residual nucleus, its four momentum \(P_0\), excitation energy \(U\) and number of excitons \(n\) equals the sum of number of particles \(p\) (from them \(p_Z\) are charged) and number of holes \(h\).

At the preequilibrium stage of reaction, we following the [GMT83] approach, take into account all possible nuclear transition the number of excitons \(n\) with \(\Delta n = +2, -2, 0\) [GMT83], which defined by transition probabilities. Only emission of neutrons, protons, deutrons, thritium and helium nuclei are taken into account.