X-ray spectromicroscopy of clusters heated by fs laser radiation.

The review of systematic investigations of X-ray radiation properties of different clusters heated by short-pulse (35-1100 fs) high-intensive (10[sup 16] - 10[sup 18] W/cm²) Ti:Sa laser radiation is presented. The cluster targets were formed by the adiabatic expansion in vacuum of an Kr or Ar gas jets produced by a pulsed valve with Laval or conical nozzles. The gas pressure is varied from 15 up to 100 bar. High spectrally (λ/δλ=4000-5000) and spatially (40-80 ·m) resolved X-Ray spectra near resonance lines (4-2 transitions) of Ne-like ions of Kr, H- and He-like ions of Ar have been obtained and detailed spectroscopic analysis was consistent with a theoretical two-temperature collisional-radiative model of irradiated atomic clusters incorporating with an effects of highly energetic electrons. The role of laser prepulse for X-ray intensity emission investigated in details. X-ray spectra radiation from plasma with electron density more than 2×10[sup 22] cm[sup -3] was observed. Big effect of fast electrons influence on the X-ray emission of He-like Ar and Ne-like Kr spectra was demonstrated. Comparison of data obtained under various experimental conditions clearly showed that for increasing X-ray output from plasma the most essential to increase size of clusters and has reasonable value of ps prepulse. [ABSTRACT FROM AUTHOR]