Multiphoton ionization of hydrogen atom by circularly-polarized electromagnetic fields

Hydrogen atom primary state multiphoton ionization was studied within the field of the intensive circularly-polarized electromagnetic wave. Quasi-classical wave functions taking partial account of both the effect of the strong electromagnetic wave and the Coulomb potential were suggested to describe the state of photoelectrons. Expressions for both angular and energy distributions of photoelectrons characterized by energy values well low the ionization potential of an undisturbed atom were obtained. It was shown that owing to the accounting of the Coulomb potential in the wave functions of the electron finite states the possibility of transition near the ionization threshold tended to the state different from zero. Besides, certain regularities of selection for multiquantum transitions within the circularly-polarized electromagnetic field were obtained naturally