The use of the x-ray absorption $K$-edge slope is investigated as a model-free diagnostic of the electronic temperature in warm dense matter. Data are reported for aluminum in a wide domain of densities (approximately one to three times the solid density) and temperatures ($\sim 0.1–10\mathrm{eV}$). Measurements are obtained from laser-shock compression where both temperature and density are independently determined from optical diagnostics. They are compared with two different theoretical approaches, respectively, based on quantum molecular dynamics and multiple scattering. Extrapolation for other absorption edges and materials is discussed.

• Received 18 May 2015

DOI:https://doi.org/10.1103/PhysRevB.92.085117