Optimization of the Q factor of the magnetic M x resonance under optical pump conditions

Optimization of parameters of the M _x resonance, which excited between Zeeman sublevels of a single HFS level of the ground state of an alkali metal in a vacuum cell in a circuit with a single beam for pumping and detection (M _x magnetometer circuit), has been carried out. A simple model taking into account all main factors controlling the resolving power of the M _x resonance (including spin-exchange broadening and absorption in a thick layer of the cell has been constructed. It is shown that the spin-resonance broadening of the resonance line is mainly determined by the requirements imposed on the optical thickness of the cell, which considerably restricts the realization of advantages of ultranarrow (<1 Hz) lines in magnetometry. The experiment confirming the efficiency of the model has been carried out.