I have a decent understanding of neutron-induced reactions in heavy nuclei (fission, capture), but less so when light nuclei are involved. I do know of Li6 + n --> He4 + T and the Li7 equivalent. Those reactions are more like nucleus splitting (fission). My question is: do neutron capture reactions for light nuclei exist? I'm mainly thinking of protium. Would it be possible to produce deuterium by having protons capture neutrons? I read about proton-neutron collisions (as a shielding measure against a neutron flux, slowing the neutrons down), but those didn't involve a forming of a new nucleus. Where do those neutrons actually go after being slowed down? Are they just around until they decay to protons?