Tunneling ionization of atoms and ions in very strong laser fields

The rate of tunneling ionization was determined as a function of the radiation intensity taking into account subbarrier and above-barrier tunneling. It was found that the Stark effect in very strong fields may stabilize atoms and ions with respect to ionization and also that the (4n – 1)th harmonics of the pump radiation are suppressed in the nonlinear response of the plasma formed by ionization.