[en] A new method of electromagnetic separation of isotopes is proposed. The results of numerical calculations of trajectories for lithium and gadolinium isotope ions are presented. The analysis of trajectories of isotope ion motion is carried out on the basis of equations obtained by solving the problem of motion of ions with different masses in constant axisymmetric radial electric and azimuthal magnetic fields in a vacuum chamber between two concentric nonmagnetic metal cylinders. It is supposed that the strengths of the electric and magnetic fields are inversity proportional to the distance from the longitudinal z axis of the system