Hot-electron influence on the x-ray emission spectra of Ar clusters heated by a high-intensity 60-fs laser pulse

The interaction of a high-intensity 60-fs laser pulse with argon clusters is investigated experimentally using methods of x-ray spectroscopy. It is shown that the plasma emission in the vicinity of He-like Ar XVII resonance line contains intense satellites caused by transitions in Li-like, Be-like, and other argon ions. It is shown that observed spectra could be explained by the presence of hot electrons in moderately ionized plasma. A simple physical model of plasma creation is proposed involving the incident picosecond prepulse followed by the main laser femtosecond pulse. Atomic kinetic calculations based on the proposed model give a good description of the experimental data.