Multiphoton population dynamics in a three-level lambda system and the   related light-scattering spectrum
  We generalize our analytic approach (Berent, M. and Parzy\'nski, R. (2009): Phys. Rev. A (80) 033834) to include the effect of strong depopulation of the initial state when considering the multiphoton population transfer and scattering of low-frequency light by a 3-level system in the lambda-type configuration. We discuss the quality of the approximations made, i.e., the adiabatic and generalized rotating-wave approximations. 
Michal Berent and Ryszard Parzynski
quant-ph physics.atom-ph