Bloch-Siegert shift in giant-dipole molecules

Abstract
The resonance-frequency shift and the energy of molecules with a large change in the permanent dipole moments between the ground and the excited levels under an intense oscillating field are investigated. It is found that the higher-order terms with respect to the Rabi frequency of the Bloch-Siegert shift cannot be neglected for molecules with a large permanent-dipole difference. Some perturbational expressions are derived, and numerical calculations are performed for various sets of parameters.