Measurement of Ionic Structure in Isochorically Heated Graphite from X-ray Thomson Scattering

We present non-collective spectrally resolved X-ray scattering measurements from isochorically heated graphite samples. The elastic and inelastic scattering spectra for the titanium He-α x-ray line at 4.75 keV yield characterization of the temperature and ionization state of the samples. It is found that the plasma theories employing a screened Coulomb potential fail to describe the ion structure of warm dense carbon plasmas and only the models accounting for the effects of the electronic configuration show good agreement with the experimental result. This agreement further suggests that the short-lived chemical bonds play an important role in determining the ion structure of warm dense graphite systems with a temperature of several electron volts.