Saturated two-photon absorption by atoms in a perturber gas

Abstract

We derive a general expression for the two-photon absorption spectrum of a state-atom excited by two monochromatic radiation fields. Collisional line-brodening effects are incorporated, and the result allows inclusion of profiles with a validity outside the impact limit. Results of previous work are recovered in the appropriate limits. Saturations affects the different lines in the two-photon absorption spectrum in a different fashion.