Time-resolved electron-temperature measurement in a highly excited gold target using femtosecond thermionic emission.

We report direct measurement of hot-electron temperatures and relaxation dynamics for peak electron temperatures between 3400 and 11000 K utilizing two-pulse-correlation femtosecond (fs) thermionic emission. The fast relaxation times ( &1.5 ps) are described by extending RT characterizations of the thermal conductivity, electron-phonon coupling, and electronic specific heat to these high electron ternperatures.