The theory of the optical Autler-Townes effect in sodium

Feneuille and Schweighofer (1975) have used a three-level model to discuss the observation of the Autler-Townes effect in a two-step resonance experiment. A numerical investigation is presented in which the effect of the neighbouring non-resonant hyperfine levels is taken into account. Firstly all the levels are treated as non-degenerate, and then degeneracy is allowed for. It is found that both the inclusion of the neighbouring states and allowance for their degeneracy cause a large change in the expected upper-state population, especially at high light intensities. It is concluded that the resonant three-level model is a poor model in this situation.