Relativistic Tunneling Effect in Ionization of Multiply Charged Ions in Multipetawatt Laser Beams

The possibility to observe the relativistic tunneling effect in ionization of multiply charged ions of heavy atoms in the field of multipetawatt laser beams is discussed. An approximate analytical formula is obtained that makes it possible to estimate the change in the ionization rate of deep levels under the action of a strong quasi-static electromagnetic field under conditions close to saturation. It is shown that the Zeeman level shift and the relativistic twist of the subbarrier electron trajectory in the magnetic field of a laser wave lead to corrections to the ionization probability that are close in magnitude to each other. These corrections become significant only at laser radiation intensities of at least 2 x 1023 W/cm2, which are expected to be achieved at multipetawatt laser facilities, including the XCELS facility. The principal scheme of the experimental observation of the deviation of the ionization rate from the values predicted by the nonrelativistic theory is discussed.