Laser Heating of Solid Matter by Light Pressure-Driven Shocks at Ultra-Relativistic Intensities

Heating by irradiation of a solid surface in vacuum with $5\times 10^{20}$ W$\mbox{cm}^{\mbox{-2}}$, 0.8 ps, 1.05 micron wavelength laser light is studied by x-ray spectroscopy of the K-shell emission from thin layers of Ni, Mo and V. A surface layer is heated to $\sim $5 keV with an axial temperature gradient of 0.6~$\mu \mbox{m}$ scale length. Images of Ni Ly$\alpha $ show the hot region has a $\sim $25~$\mu \mbox{m}$ diameter. Collisional particle-in-cell simulations based on density profiles from hydro-models suggest that light pressure compresses the preformed plasma and drives a shock into the solid.