Nonlinear inverse bremsstrahlung and the harmonic generation in a plasma

The phenomena of nonlinear bremsstrahlung absorption and generation of five first odd harmonics are investigated for a plasma photoionized in the Bethe regime of the suppression of the ionization barrier, in which case the velocity distribution of plasma electrons coincides with the distribution of atomic electrons. The partial nonlinear conductivities are obtained. A comparison is made between the features of the absorption and the effectiveness of harmonic generation in two different cases when atomic electrons before ionization are in the ns- or np-states. It was demonstrated that the nonlinear effective collision frequencies (NECF) have unique form in the limit of the high intensity of the pump field. On the other side NECF have the pump field dependencies near their maximum values which are different for the case of s-states and p-states. These dependencies are characterized by especial scaling functions, which give the dependencies on the pump field intensity, the value of the principal quantum number of the pre-excited states of atoms and harmonics numbers.