Meson exchange currents in few-nucleon systems and radiative capture of neutrons

Three beams of the high flux reactor HFR in Petten are being used for nuclear physics research primarily aiming at a test of the validity of models describing mesons in nuclei. Mesonic exchange currents (MEC) manifest themselves in the cross section as well as in the channel spin interference of radiative capture of neutrons in H, D and 3 He. Experiments with polarized neutrons and polarized target nuclei clearly indicate the existence of MEC. In the low cross section reaction 3 He(n, gamma ), which partly proceeds by double-photon emission, regular internucleon contributions are much more suppressed than MEC.