HIGH-ORDER HARMONIC-GENERATION BY ELECTRON-PROTON RECOMBINATION

Classical models have been proven to successfully explain some general features of the harmonic generation in the tunnelling limit. In parti cular, it can be shown that the energies of the produced harmonics are bounded by an upper limit given by I(p) + 3.17U(p). In this paper we show that this limit can be exceeded by considering the special case i n which the harmonics are generated when the ionized electrons are cap tured not by the parent ion but by some neighbouring ion located at a given distance.