Magnetic field effect on laser isotope separation based on polarization selection rules

Excitation dynamics of atoms by linearly polarized lasers were analyzed for J = 2 --> 2 --> 1 --> 0 multistep transition under a magnetic field. The time evolution of the population in each magnetic substate was calculated by solving the rate equations under the condition where the atomic alignment is gradually destroyed by the precession motion of the angular momentum around the magnetic field. Isotopic selectivity in the laser isotope separation based on the polarization selection rules was discussed. It has been found that a relatively small magnetic field may cause a degradation of selectivity in the case of Gd and the magnetic field should be kept as small as the terrestrial magnetic field when the laser polarization is perpendicular to the magnetic field.