HIGH-HARMONIC GENERATION AFFECTED BY A STATIC ELECTRIC-FIELD

High-harmonic generation (HHG) by a zero-range atom illuminated by a l inearly polarized laser pulse in the presence of an additional static electric field is investigated theoretically. It is shown that the cut off of the harmonic spectrum can be controlled with the help of the st atic field. The plateau can be extended far beyond the usual cutoff en ergy of \E-0\ + 3.17U(p). In some cases, a second plateau appears that extends to still higher energies. The cutoff energies of the first as well as the second plateau are correctly predicted by a classical mod el. However, the static field strengths required for these manipulatio ns of the HHG cutoff are much larger than experimentally available.