Extreme ultraviolet emission from dense plasmas generated with sub-10-fs   laser pulses
  The extreme ultraviolet (XUV) emission from dense plasmas generated with sub-10-fs laser pulses with varying peak intensities up to 3*10^16 W/cm^2 is investigated for different target materials. K shell spectra are obtained from low Z targets (carbon and boron nitride). In the spectra a series limit for the hydrogen and helium like resonance lines is observed indicating that the plasma is at high density and pressure ionization has removed the higher levels. In addition, L shell spectra from titanium targets were obtained. Basic features of the K and L shell spectra are reproduced with computer simulations. The calculations include hydrodynamic simulation of the plasma expansion and collisional radiative calculations of the XUV emission. 
J. Osterholz, F. Brandl, M. Cerchez, T. Fischer, D. Hemmers, B.   Hidding, A. Pipahl, G. Pretzler, S.J. Rose and O. Willi