Paramagnetism of gases in the radiation field

Abstract

The behaviour of paramagnetic gas (alkaly metal vapour) resonantly interacting with monochromatic radiation, in the presence of a longitudinal constant magnetic field is investigated. The method of quasienergy states and the statistic distribution over the sublevels of atomic ground state in the magnetic field are used. The expression for magnetization are derived as a function of constant magnetic field and of electromagnetic field of different polarizations (the nonlinear inverse Faraday effect particularly) for the case of two-level ( j 1 = 1 2 → j 2 = 1 2 , 3 2 transitions) and the three-level ( j 1 = 1 2 → j 2 = 3 2 → j 3 = 1 2 transitions, two-photon resonance) atoms. In the case of two-level atoms an interval of electromagnetic field intensity exists for any given magnetic field where the paramagnetic gas becomes diamagnetic. In the case of two-photon resonance magnetic properties of gas does essentially depend on relative sign of one- and two-photon resonance detunings. When these signs coincide, the atom which behaves like the two-level and in the opposite case the magnetization is described by the Langevin-formula.