Temperature Equilibration in Tantalum

Understanding the behavior of materials with significantly different electron and ion temperatures is important for much of the experimental and theoretical work on dense plasmas. We present measurements of electron-ion temperature equilibration in proton-heated tantalum, under warm dense matter conditions. Our results agree with theoretical predictions calculated from {\it ab initio} molecular dynamics simulations, as well as with those from the Fermi Golden Rule approach often used for dense plasmas. However, the fast relaxation time observed in the experiment contrasts with much slower equilibration found in particle-heated carbon, indicating that the energy flow pathways in warm dense matter are far from being fully understood.