Multiple-quantum radio-frequency spectroscopy of atoms: Application to the metrology of geomagnetic fields

The evolution of the radio-frequency magnetic resonance spectrum of optically oriented potassium atoms in terrestrial magnetic fields as a function of the amplitude of the alternating magnetic field H ₁ is investigated theoretically and experimentally. It is shown that among the set of observed n-quantum resonances which satisfy the selection rules ΔF=0 and Δm _F±n (n is an integer), there is one resonance with the highest multiplicity n=4 (m _F=2⇔m _F=−2), which has exceptional properties. These qualities make this resonance a candidate for use in a weak-field quantum magnetometer with record-high characteristics. A preliminary investigation of an experimental model of a four-quantum potassium magnetometer is performed. Zh. Tekh. Fiz. 69, 27–30 (September 1999)