X-ray spectral diagnostics of laser harmonic generation in the interaction of relativistic femtosecond laser pulses with clusters

It is shown that the production of X-ray emission spectra in the interaction of high-intensity laser radiation with cluster tar- gets may be affected by the bichromatic oscillating electric field arising from the generation of the second harmonic of laser radia- tion. A technique is proposed for diagnosing harmonic generation in laser – cluster interactions using the spectral line profiles of multi- ply charged helium ions. The efficiency of second harmonic genera- tion at a laser intensity of 3 × 1018 W cm–2 is shown to amount to about 2 %