Neutron capture is a kind of nuclear reaction in which an atomic nucleus collides with one or more neutrons and they merge to form a heavier nucleus. Since neutrons have no electric charge, they can enter a nucleus more easily than charged particles which are repelled by electrostatic repulsion.Neutron capture plays an important role in the cosmic nucleosynthesis of heavy elements. In stars, it can proceed in two ways - as a rapid process (an r-process) or a slow process (an s-process). By neutron capture, nuclei of masses greater than 56 can be formed that could not be formed by thermonuclear reactions, i.e., by nuclear fusion.
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The reaction that occurs when a nucleus captures a neutron. The probability that a given material will capture a neutron is proportional to its neutron capture cross section and depends on the energy of the neutrons and the nature of the material.