Line Positions in Warm Dense Matter

Transition energies in dense plasmas, in which an atom is excited from some initial state to a final state, are challenging to model due to the need for an accurate treatment of both atomic and plasma physics. Experiments have been carried out at the LCLS that measured the K-edge and K-alpha emission from magnesium, aluminum, and silicon plasmas [Ciricosta et al, Nat. Comm. 2016]. We use a modified version of the Tartarus average atom code [Starrett et al, CPC 2019] to model ions in dense plasmas and calculate the K-edges and K-alpha to compare with these experiments. We find that our calculations agree with the experiments if we assume K-shell ionization from a cold plasma (1eV), and the subsequent K-alpha de-excitation from a heated plasma. The results give insight into the timescale and temperature dependence of electron transitions and ionization, as well as the plasma effects that must be taken into consideration.