  Population of levels of the hyperfine and fine split ground state of an atom
is affected by radiative transitions induced by anisotropic radiation flux.
Such aligned atoms precess in the external magnetic field and this affects
properties of polarized radiation arising from both scattering and absorption
by atoms. As the result the degree of light polarization depends on the
direction of the magnetic field. This provides a perspective tool for studies
of astrophysical magnetic fields using optical and UV polarimetry. We provide
calculations for several atoms and ions that can be used to study magnetic
fields in interplanetary medium, interstellar medium, circumstellar regions and
quasars.
