The region of light nuclei houses some of the neutron standards [36]. Starting from proton-neutron scattering below 20 MeV up to carbon-neutron scat­tering, all cross sections can be calculated by the methods described above, at least in principle, in case suitable nucleon-nucleon potentials are given. In the form of the RGM n-p scattering is just potential scattering, hence, any calculation just reflects how well the extracted potential was fitted to the original data.

The next simplest reaction is 3He (n, p)3H, which has 4He as compound nucleus. For this A = 4 system realistic nucleon-nucleon forces are feasi­ble, whereas for all heavier systems one has to rely on simplified, so-called effective forces. To demonstrate the differences, advantages and disadvan­tages I discuss in some detail in the following the 4He-system and the 7Li — system, which contains another standard reaction 6Li (n, t)4He. The reaction 10B(n, a) closes this section.