Effect of time reversal in the magnetization of an atom by a resonant light pulse

It is shown that the even dependence of the light-induced magnetic moment on the detuning ω-ωba from resonance in the case of a circularly polarized pulse and an isotropic initial state of the atom and the odd dependence on ω-ωba in the case of a linearly polarized pulse and an anisotropic initial state in the form of alignment of the atom are consequences of the symmetry under time reversal t→−t and of the initial conditions at time t=0. In a number of cases, this fundamental law makes it possible to determine the vector properties of a light-induced magnetic moment and its dependence on the time t and ω-ωba without solving the equation for the density matrix in detail and without calculating the sum over the projections of the angular momenta in the formula for the magnetization of an atom by light.