Atomic antenna: Nonlinear scattering of a superatomic-intensity laser pulse

A semiclassical model of high harmonic generation upon ionization by suppressing the atomic barrier is developed. The spreading of the wave packet of an ionized electron, which is chosen in the form of a Gaussian distribution, is considered. The quantum nature of the process is taken into account by the initial discrete level of the electron, and the finite wave packet spreading occurs in the continuum. After its detachment from the atom, the electron is assumed to be free and moving under the action of the laser pulse field and the Coulomb interaction of the electron with the atomic core can be treated as a perturbation. The radiation from the electron is calculated from its acceleration expressed in terms of the average force of interaction of the electron with the Coulomb center of the atom.