Two-quantum magnetic resonance driven by a comb-like rf field

We report a new method for excitation of magnetic resonance in an optically aligned atomic ensemble. It employs a comb-like rf field acting on the end sublevels of the F g = 1 state separated by the doubled Zeeman frequency. This approach provides a resonance without substructures associated with the quadratic Zeeman shift. A theoretical explanation of the effect is given in terms of the two-quantum transition | F g = 1 , m F g = − 1 ⟩ ⇆ | F g = 1 , m F g = 1 ⟩ and is corroborated by an experiment with 87 R b atoms. Possible advantages of the approach and its range of applicability are discussed.