X-ray emission spectra of the plasma produced by an ultrashort laser pulsein cluster targets

The first observation of x-ray emission spectra of multiply charged ions in the plasma produced by a 35-fs laser pulse with an intensity up to 10(17) W cm(-2) in CO2 and Kr gas jet targets is reported. The emission in the wav elength ranges of the 1snp - 1s(2) (n = 3 - 6) transitions of OVII ions and the Ly(alpha) Line of OVIII ions, as well as of the (2s(1/2)2P(6) 3P(3/2)) (1) -2s(2)2p(6 1)S(0) and (2s(1/2)2p(6)3P(1/2))(1)- 2S(2)2p(6 1)S(0) lines of Ne-like KrXXVII ions testifies that the highly ionised plasma is formed by collision processes in clusters. Modelling the shape of the spectral lin es of oxygen ions by including the principal mechanisms of broadening and a bsorption in optically dense plasmas reveals that the main contribution to the time-integrated intensity is made by the plasma with the parameters N-e = (2 - 20) x 10(20) cm(-3) and T-e = 100 - 115 eV.