Coherent backscattering of intense light by cold atoms with degenerate   energy levels: Diagrammatic treatment
  We present a generalization of the diagrammatic pump-probe approach to coherent backscattering (CBS) of intense laser light for atoms with degenerate energy levels. We employ this approach for a characterization of the double scattering signal from optically pumped atoms with the transition $J_g\rightarrow J_e=J_g+1$ in the helicity preserving polarization channel. We show that, in the saturation regime, the internal degeneracy becomes manifest for atoms with $J_g\geq 1$, leading to a faster decrease of the CBS enhancement factor with increasing saturation parameter than in the non-degenerate case. 
V.N. Shatokhin, R. Blattmann, T. Wellens, A. Buchleitner
quant-ph physics.atom-ph