The contribution of Erwin Schroedinger to the calculation of the extinction probability and its comparison with the work of Lenard Pal

The concept of the extinction probability transcends neutron behaviour and can be found in many areas of science, engineering, biology and topically in epidemiology. In this work we concentrate on neutron applications and in particular to the history of the development of the subject. The extinction probability is the probability that a neutron injected at some point in a fissile medium will eventually become extinct. We discuss a relatively little known paper by Erwin Schroedinger, published in 1945 in the Proceedings of the Royal Irish Academy. The work described by Schroedinger has some similarities with the later work of Lenard Pal but we believe that Schroedinger has omitted a vital part of the argument: in the finite medium case the scattering cross section of the fissile material does not enter his calculations