In 1949, Feshbach and collaborators proposed the optical model of nuclear reactions, in which the atomic nucleus isseen as an opaque sphere capable of reflecting or absorbing the incident particles, where the potential which describesthe reaction has a complex term, the latter being responsible for the absorption. The mathematical structure of theoptical potential is complicated, being the result of a sum over all contributions to interaction energies of the partnersinvolved in the reaction. It can also be obtained by quantum mechanical formalism developed by Feshebach, but that isonly approximate.