T. G. White, J. Vorberger, C. R. D. Brown, B. J. B. Crowley, P. Davis, S. H. Glenzer, J. W. O. Harris, D. C. Hochhaus, S. Le Pape, T. Ma, C. D. Murphy, P. Neumayer, L. K. Pattison, S. Richardson, D. O. Gericke, G. Gregori
Creating non-equilibrium states of matter with highly unequal electron and lattice temperatures allows unsurpassed insight into the dynamic coupling between electrons and ions through time-resolved energy relaxation measurements. Recent studies on low-temperature laser-heated graphite suggest a complex energy exchange when compared to other materials. To avoid problems related to surface preparation, crystal quality and poor understanding of the energy deposition and transport mechanisms, we apply a different energy deposition mechanism, via laser-accelerated protons, to isochorically and non-radiatively heat macroscopic graphite samples up to temperatures close to the melting threshold. Using time-resolved x ray diffraction, we show clear evidence of a very small electron-ion energy transfer, yielding approximately three times longer relaxation times than previously reported. This is indicative of the existence of an energy transfer bottleneck in non-equilibrium warm dense matter.
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http://arxiv.org/abs/1303.1402
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