Harmonic generation for atoms in fields of varying ellipticity: Single-active-electron model with Hartree-Fock potential

We propose a theoretical procedure for calculating harmonics yield from atoms based on the solution of a three-dimensional time-dependent Schrödinger equation. The atomic system is described by means of the Hartree-Fock potential, including the exchange interaction. We present results for the harmonics generation in lithium and rubidium in situation when ellipticity of the driving laser changes with time. These results show that harmonics are formed primarily at the intervals of time when the driving laser field has nearly zero ellipticity. This can be used for generation of short (hundreds of attoseconds) bursts of radiation.