The
nuclear cross section of a nucleus is used to characterize the
probability that a nuclear reaction will occur. The concept of a nuclear cross section can be quantified physically in terms of "characteristic area" where a larger area means a larger probability of interaction. The standard unit for measuring a nuclear cross section (denoted as s) is the
barn, which is equal to 10
-28 m² or 10
-24 cm². Cross sections can be measured for all possible interaction processes together, in which case they are called total cross sections, or for specific processes, distinguishing
elastic scattering and
inelastic scattering; of the latter, amongst
neutron cross sections the
absorption cross sections are of particular interest.