Absorption of VUV-FEL Radiation in Warm Dense Matter

The interaction of ultra-intense 50 fs VUV-beams with solid-density metal and plasma targets has been simulated, solving Maxwell$'$s equations in one-dimensional geometry. An explicit dielectric function is derived describing photo-ionization in addition to collisional absorption by conduction electrons. As an example, heating of thin aluminum foils up to electron temperatures of 450 eV is discussed, including results on emission spectra during and after the heating. The simulations correspond to experiments now in progress at DESY in Hamburg, using the new VUV Free Electron Laser