I. Sainz, A.B. Klimov and C. Saavedra
JOURNAL OF OPTICS B-QUANTUM AND SEMICLASSICAL OPTICS 6, 11 (2004)
Effective resonant quantum atom-field interactions are studied. These resonant interactions are induced by the presence of an external classical driving field. An adequate choice for frequencies of the driving field produces nonlinear effective Hamiltonians both for atom-field and for spin-spin interactions. It is shown that the exact numerical evolution for each resonance condition is well described by the corresponding effective Hamiltonian.