Two-scale angular-momentum evolution induced by elliptically polarized resonance radiation for a two-level atom with J g → J e =J g +1 optical transition in a constant magnetic field

Abstract

The dynamics of a two-level atom with optical transition J g → J e =J g + 1 under the action of elliptically polarized resonance radiation in the presence of a constant field directed along the radiation wave vector is studied in the approximation of a semiclassical description of the angular momentum orientation. It is shown that the atomic distribution over the angular momentum orientation exhibits a two-scale time evolution. At the first stage, after the beginning of irradiation, the angular momenta of atoms get oriented (over comparatively short time intervals) along the magnetic field, as well as in the opposite direction, depending on their initial orientation and the ellipticity of radiation. At the second (longer) stage, the redistribution of atoms takes place, as a result of which they are oriented predominantly in one of the above directions. The duration of the second stage is an exponential function of angular momentum J.