High-temperature plasma produced on a free liquid surface by femtosecond laser pulses

The plasma formed by femtosecond laser radiation with an intensity higher than 10{sup 16} W cm{sup -2} at the free surface of a liquid (VM-1 vacuum oil) in vacuum has parameters which are similar to the parameters of the high-temperature plasma produced at the surface of a solid target. The hot-electron temperature (derived from X-ray and ion time-of-flight measurements) is 6 {+-} 3 keV for the VM-1 oil target and 4 {+-} 1 keV for a crystal silicon target. The optical diagnostics of the relaxation of the liquid target surface revealed that the limiting laser pulse-repetition rate whereby the interaction takes place with the unperturbed liquid surface may be as high as 10 Hz. (interaction of laser radiation with matter. laser plasma)