Our experimental knowledge of the nucleon-nucleon-gamma production is irregular. Thc proton-proton systcm has been thoroughly studied (25,26) because it is experimentally the simplest. A good measurement of the momenta and energies of the two protons, after scattering, is basically sufficient to describe the reaction. The neutron-neutron system is unknown, for obvious reasons. Our knowledge of the neutron-proton gamma process is poor (27-30) because of the small intensity and poor resolution of neutron beams. Furthermore the neutron and photon detec tors are more difficult to build and less efficient than proton detectors.

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