Stark-chirped rapid adiabatic passage among degenerate-level manifolds

We generalize Stark-chirped rapid adiabatic passage (SCRAP) to the case of two and three degenerate-level manifolds. The analysis of a degenerate-level system is facilitated by its subdivision into a set of smaller independently evolving subsystems corresponding to the minimal-sized invariant subspaces of the Hamiltonian. Population transfer from the starting to the final level is examined for different types of the invariant subspaces depending on the presence of dark states. It is shown that the complete transfer is feasible if the initial state is prepared into specific coherent superpositions. Our formalism is applicable to the general case of arbitrary numbers of degenerate states within each level and arbitrary couplings of the appropriate transitions. It represents a generalization of well-known Morris-Shore transformation to the case when the removed degeneracy of the sublevels leads to detuning from two-photon resonance. We give the application of the SCRAP formalism to the Rb-87 atom.