Measurement of the analogous Zeeman shift using a low-velocity intense source

The energy shift of an atom due to its interaction with the oscillating electric field of an electromagnetic wave, or a laser light, is called the ac Stark shift. It has been studied both in the field of precision spectroscopy and atom optics. When the laser intensity is not constant spatially, its gradient gives rise to a dipole force. The force was used either to trap atoms in an optical trap or to reflect or guide atoms. We studied the ac Stark effect taking into account the fine structure of an alkali atom. We found that when the laser light is circularly polarized and properly detuned between the D1 and D2 transitions, the ac Stark shift can take the form of a pure Zeeman shift, hence the name analogous Zeeman shift.