The likelihood of a neutron absorption is represented by the absorption cross section as σa. The relative likelihoods of an absorption reaction or a neutron scattering are represented by dividing the total cross section into scattering and absorption cross sections:
σt = σs + σa
Given a collision, σa / σt is the probability that the neutron will be
absorbed and σs / σt is the probability that the neutron will be scattered.