Electron-ion equilibration in superheated gold
- Travis D. Griffin
- Dirk O. Gericke
- Daniel Haden
- Hae Ja Lee
- Eric Galtier
- Eric Cunningham
- Dimitri Khaghani
- Michael Larsen
- Lennart Wollenweber
- Ben Armentrout
- Carson Convery
- Karen Appel
- Gilliss Dyer
- Luke B. Fletcher
- Sebastian Göde
- J. B. Hastings
- Jeremy Iratcabal
- Emma E. McBride
- Jacob Molina
- Giulio Monaco
- Landon Morrison
- Hunter Stramel
- Sameen Yunus
- Ulf Zastrau
- Siegfried H. Glenzer
- Gianluca Gregori
- Bob Nagler
- Thomas G. White
2026-06-18
Electron-ion equilibration dynamics in samples driven into superheated states with multi-eV electron temperatures represent a fundamental process in nonequilibrium physics. A clear picture of the evolving ion temperature is essential for understanding the strength of the electron-ion coupling. However, direct, model-independent measurements of the ion temperature in laser-irradiated samples have remained experimentally elusive. Using inelastic X-ray scattering with meV-resolution in gold samples, the ion response to ultrafast heating by the hot electrons can be resolved, quantifying the electron-ion equilibration dynamics. We report measurements revealing a strongly enhanced energy transfer rate compared to that in weakly excited gold. Moreover, we obtain a quasi-constant electron-ion coupling at the highly elevated electron temperatures. These results place new constraints on electron-ion energy transfer in warm dense matter and establish a path toward quantitative benchmarking of models for nonequilibrium dynamics.