Fermi’s favorite figure: the history of the pseudopotential concept in atomic physics and neutron physics

Abstract In the early 1930’s, Fermi wrote two papers in which he introduced concepts of “scattering length” and “pseudopotential.” Since that time, these terms have become universally associated with low energy scattering phenomena. Even though are very different—one atomic physics, other neutron physics—a simple figure underlies both. The appears many times Fermi’s work. We review how came about briefly discuss modern developments work initiated remarkable papers.