CHARACTERISTIC FEATURES OF THE X-RAY-SPECTRA OF A PLASMA PRODUCED BY HEATING CO2 CLUSTERS BY INTENSE FEMTOSECOND LASER-PULSES WITH LAMBDA=0.8 AND 0.4 MU-M

The x-ray spectra of a plasma produced by heating CO2 clusters with in tense femtosecond laser pulses with lambda = 0.8 and lambda = 50.4 are mm mm investigated. Spatially resolved x-ray spectra of the cluster p lasma are obtained. The observed characteristic features of the x-ray emission spectra show unequivocally that such a plasma contains quite a large relative number of ions (similar or equal to 10(-2)-10(-3)) wi th energies of 0.1- 1 MeV. The contour of the OVIII Ly(alpha) line is found to have characteristic features that are especially conspicuous when the clusters are heated with second-harmonic pulses. These featur es cannot be explained by any mechanisms known to the authors. (C) 199 8 American Institute of Physics. [S0021-3640(98)00418-6]