Resonant enhancement of harmonic generation in argon at 248 nm

We present results of accurate ab initio Floquet calculations of lower-order harmonic generation by argon at the KrF laser fundamental frequency which exhibit large enhancement of the third, fifth and seventh harmonics at intensities corresponding to field-atom resonances. The resonant effects occur at relatively low laser intensities. These are the first reported results for a complex atom taking full account of electron correlation and give a quantitative description of the resonant enhancement. We infer that similar enhancements will occur for other multi-electron atomic systems. The single-atom response calculations demonstrate the importance of resonant enhancement of harmonic generation in multi-electron atoms and suggest a possible low-cost method of sustainable harmonic generation.