Understanding XANES spectra of two-temperature warm dense copper using <i>ab initio</i> simulations
N. Jourdain, V. Recoules, L. Lecherbourg, P. Renaudin, F. Dorchies
Abstract
Using ab initio molecular-dynamics simulations combined with linear-response theory, we studied the x-ray absorption near-edge spectra (XANES) of a two-temperature dense copper plasma. As the temperature increases, XANES spectra exhibit a pre-edge structure balanced by a reduction of the absorption just behind the edge. By performing systematic simulations for various thermodynamic conditions, we establish a formulation to deduce the electronic temperature ${T}_{e}$ directly from the spectral integral of the pre-edge that can be used for various thermodynamic conditions encountered in a femtosecond heating experiment where thermal nonequilibrium and expanded states have to be considered.