Resonances induced in H atoms by the high-intensity 800 nm laser field

A hydrogen atom exposed to a linearly polarized laser field with a wavelength of 800 nm and intensity varying from 1013 to 1014Wcm-2 is studied using non-perturbative non-Hermitian Floquet theory. The rate of ionization is calculated and the resonant enhancements are analysed by determining the composition of the ground and resonant-state wave functions. A map of resonant-state quasienergies is presented. The electronic density of the quasi-energy ground state versus the electron coordinate is analysed too. We conclude that the decay of an atom in a low intensity non-resonant laser field occurs from the asymptotically distant part of the ground state. For a higher intensity, the ionization proceeds using the mechanism of interchanging the character of the ground state with a radiatively coupled excited state(s). The process of electron emission is governed by the excited-bound-state part of the resonance wave function. With an increase of intensity, the electron is ionized at smaller distances from the nucleus.