A reduced coupled-mode description for the electron-ion energy relaxation in dense matter

¹  Clarendon Laboratory, Department of Physics, University of Oxford - Parks Road, Oxford OX1 3PU, UK
²  Central Laser Facility, Rutherford Appleton Laboratory - Didcot OX11 0QX, UK
³  Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick Coventry CV4 7AL, UK

Received: 31 March 2008
Accepted: 14 May 2008

Abstract

We present a simplified model for the electron-ion energy relaxation in dense two-temperature systems that includes the effects of coupled collective modes. It also extends the standard Spitzer result to both degenerate and strongly coupled systems. Starting from the general coupled-mode description, we are able to solve analytically for the temperature relaxation time in warm dense matter and strongly coupled plasmas. This was achieved by decoupling the electron-ion dynamics and by representing the ion response in terms of the mode frequencies. The presented reduced model allows for a fast description of temperature equilibration within hydrodynamic simulations and an easy comparison for experimental investigations. For warm dense matter, both fluid and solid, the model gives a slower electron-ion equilibration than predicted by the classical Spitzer result.