Coulomb effects in photoionization of H atoms irradiated by intense laser fields

We theoretically study the Coulomb effects on the photoionization processes of the H atom irradiated by the intense laser fields with circular and linear polarizations. For this purpose we represent the final continuum state by the Coulomb-Volkov state. Total ionization rates, photoelectron energy spectra, and angular distribution of photoelectrons are calculated and compared with those obtained using the Volkov state. We find that how much the Coulomb field influences the ionization dynamics depends on the momentum of photoelectrons, among which the photoelectron angular distributions in the linearly polarized laser field represent the most striking difference.