  The interaction of 32.5 and 6 nm ultrashort X-ray pulses with the solid
materials B4C, SiC and Si is simulated with a non-local thermodynamic
equilibrium (NLTE) radiation transfer code. We study the ionization dynamics as
function of depth in the material, modifications of the opacity during
irradiation and estimate crater depth. Furthermore, we compare the estimated
crater depth with experimental data, for fluences up to 2.2 J/cm2. Our results
show that at 32.5 nm irradiation, the opacity changes with less than a factor
of 2 for B4C and Si and a factor of 3 for SiC, for fluences up to 200 J/cm2. At
a laser wavelength of 6 nm, the model predicts a dramatic decrease in opacity
due to the weak inverse bremsstrahlung, increasing the crater depth for high
fluences.
