4. METHOD OF SOLUTION
The model adopted is based on the following assumptions:
i) Compound nucleus processes only take place and the cross section for compound nucleus formation is equal to the reaction cross section. De-excitation happens through successive evaporations of neutrons, protons, alpha particles and gamma rays. More than three successive emissions are not admitted.
ii) The nucleus can be described as a perfect gas of nucleons whose level density is given by the shifted Fermi gas model.
iii) If the residual nucleus after the second emission has an excitation energy above the neutron emission threshold, a neutron is emitted.