Landau–Zener formula
The Landau–Zener formula is an analytic solution to the equations of motion governing the transition dynamics of a two-state quantum system, with a time-dependent semi-classical Hamiltonian varying such that the energy separation of the two states is a linear function of time. The formula, giving the probability of a non-adiabatic transition between the two adiabatic energy states, was published separately by Lev Landau, Clarence Zener, Ernst Stueckelberg, and Ettore Majorana, in 1932.