Coulomb correction to the ionization rate of atoms in high-frequency intense laser fields

A Coulomb correction to the rate of multiphoton ionization of atoms and positive ions in intense high-frequency laser fields is found using the imaginary time method for a subbarrier trajectory and Kapitza method for description of motion in a rapidly oscillating field. The obtained results cover the domain of parameters opposite to the well-studied low-frequency tunneling limit. We show that the Coulomb correction enhances the ionization rate up to several orders in magnitude. Application of the obtained results for description of multiphoton ionization in intense ultraviolet laser pulses is briefly discussed.