A
seed nucleus is an
isotope that is the starting point for any of a variety of fusion
chain reactions. The mix of nuclei produced at the conclusion of the chain reaction generally depends strongly on the relative availability of the seed nucleus or nuclei and the component being fused--whether
neutrons as in the
r-process and
s-process or protons as in the
rp-process. A smaller proportion of seed nuclei will generally result in products of larger
mass, whereas a larger seed-to-neutron or seed-to-proton ratio will tend to produce comparatively lighter masses.