Dielectric function of warm dense gold

Single-state measurements of the broadband (450-800 nm) dielectric function of gold using a supercontinuum probe are reviewed. These measurements have demonstrated the first evidence of the existence of band structure in ultrathin gold foils isochorically heated by a femtosecond laser pulse to energy densities of 10(6)-10(7) J/kg. The Drude component of the dielectric function increases with energy density while the interband component shows both enhancement and redshift. Ab initio molecular-dynamics calculations based on thermalized electrons cannot reproduce the experimental results, suggesting a non-Fermi distribution of excited electrons. (C) 2008 American Institute of Physics.